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1. Characterising the Apertif primary beam response

Author: H. Dénes, K. M. Hess, E. A. K. Adams, A. Kutkin, R. Morganti, J. M. van der Hulst, T. A. Oosterloo, V. A. Moss, B. Adebahr, W. J. G. de Blok, M. V. Ivashina, A. H. W. M. Coolen, S. Damstra, B. Hut, G. M. Loose, D. M. Lucero, Y. Maan, Á. Mika, M. J. Norden, L. C. Oostrum, D. J. Pisano, R. Smits, W. A. van Cappellen, R. van den Brink, D. van der Schuur, G. N. J. van Diepen, J. van Leeuwen, D. Vohl, S. J. Wijnholds, J. Ziemke, Ministerio de Ciencia e Innovación (España), European Commission, European Research Council, German Research Foundation, Astronomy, and Kapteyn Astronomical Institute
Subjects: Astrophysics::Instrumentation and Methods for Astrophysics, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Surveys, Methods: observational, Space and Planetary Science, Instrumentation: interferometers, Physics::Accelerator Physics, Instrumentation: detectors, Astrophysics - Instrumentation and Methods for Astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), Astrophysics::Galaxy Astrophysics, Telescopes
Abstract: Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited., Context. Phased array feeds (PAFs) are multi-element receivers in the focal plane of a telescope that make it possible to simultaneously form multiple beams on the sky by combining the complex gains of the individual antenna elements. Recently, the Westerbork Synthesis Radio Telescope (WSRT) was upgraded with PAF receivers to carry out several observing programs, including two imaging surveys and a time-domain survey. The Apertif imaging surveys use a configuration of 40 partially overlapping compound beams (CBs) simultaneously formed on the sky and arranged in an approximately rectangular shape. Aims. This work is aimed at characterising the response of the 40 Apertif CBs to create frequency-resolved I, XX, and YY polarization empirical beam shapes. The measured CB maps can be used for the image deconvolution, primary beam correction, and mosaicking processes of Apertif imaging data. Methods. We used drift scan measurements to measure the response of each of the 40 Apertif CBs. We derived beam maps for all individual beams in I, XX, and YY polarisation in 10 or 18 frequency bins over the same bandwidth as the Apertif imaging surveys. We sampled the main lobe of the beams and the side lobes up to a radius of 0.6 degrees from the beam centres. In addition, we derived beam maps for each individual WSRT dish. Results. We present the frequency and time dependence of the beam shapes and sizes. We compared the compound beam shapes derived with the drift scan method to beam shapes derived with an independent method using a Gaussian Process Regression comparison between the Apertif continuum images and the NRAO VLA Sky Survey (NVSS) catalogue. We find a good agreement between the beam shapes derived with the two independent methods. © H. Dénes et al. 2022., This work makes use of data from the Apertif system installed at the Westerbork Synthesis Radio Telescope owned by ASTRON. ASTRON, the Netherlands Institute for Radio Astronomy, is an institute of the Dutch Research Council (“De Nederlandse Organisatie voor Wetenschappelijk Onderzoek, NWO). K.M.H. acknowledges financial support from the State Agency for Research of the Spanish Ministry of Science, Innovation and universities through the “Center of Excellence Severo Ochoa” awarded to the Instituto de Astrofísica de Andalucía (SEV-2017-0709) from the coordination of the participation in SKA-SPAIN, funded by the Ministry of Science and innovation (MICIN). EAKA is supported by the WISE research programme, which is financed by the Netherlands Organization for Scientific Research (NWO). J.M.vd.H. and K.M.H. acknowledge funding from the European Research Council under the European Union’s Seventh Framework Programme (FP/2007-2013)/ERC Grant Agreement No. 291531 (‘HIStoryNU’). B.A. acknowledges funding from the German Science Foundation DFG, within the Collaborative Research Center SFB1491 “Cosmic Interacting Matters - From Source to Signal”. Y.M., L.C.O., and R.S. acknowledge funding from the European Research Council under the European Union’s Seventh Framework Programme (FP/2007-2013)/ERC Grant Agreement No. 617199. J.vL. acknowledges funding from Vici research programme ‘ARGO’ with project number 639.043.815, financed by the Dutch Research Council (NWO). D.V. acknowledges support from the Netherlands eScience Center (NLeSC) under grant ASDI.15.406. This research has made use of NUMPY (van der Walt et al. 2011), SCIPY (Virtanen et al. 2020), ASTROPY, a community-developed core PYTHON package for Astronomy (Astropy Collaboration 2013, 2018; http://www.astropy.org), and scikit-learn (Pedregosa et al. 2011). Data availability: The FITS format CB maps generated from the drift scan observations are available from zenodo as two data sets. Frequency setting 1130-1430 MHz DOI: https://doi.org/10.5281/zenodo.6615555, 1220–1520 MHz DOI: https://doi.org/10.5281/zenodo.6544109. The raw drift scan data are stored on the Apertif Long Term Storage and can be requested for further analysis trough the ASTRON helpdesk (https://support.astron.nl/sdchelpdesk). The observation taskIDs used for the individual drift scan beam maps are listed within aperPB (https://github.com/apertif/aperPB, https://doi.org/10.5281/zenodo.6544109) in the task_id_lists directory with the following file names: task_ids_{beamID}.txt. The GP CB maps are available within the Apertif DR1, trough the ASTRON Virtual Observatory (https://vo.astron.nl/; detailed documentation on the Apertif DR1 is available here: http://hdl.handle.net/21.12136/B014022C-978B-40F6-96C6-1A3B1F4A3DB0).
Published: 2022

2. Continuum source catalog for the first APERTIF data release

Author: A. M. Kutkin, T. A. Oosterloo, R. Morganti, E. A. K. Adams, M. Mancini, B. Adebahr, W. J. G. de Blok, H. Dénes, K. M. Hess, J. M. van der Hulst, D. M. Lucero, V. A. Moss, A. Berger, R. van den Brink, W. A. van Cappellen, L. Connor, S. Damstra, G. M. Loose, J. van Leeuwen, Y. Maan, Á. Mika, M. J. Norden, A. R. Offringa, L. C. Oostrum, D. van der Schuur, D. Vohl, S. J. Wijnholds, J. Ziemke, Astronomy, Kapteyn Astronomical Institute, Ministerio de Ciencia e Innovación (España), European Commission, European Research Council, German Research Foundation, and High Energy Astrophys. & Astropart. Phys (API, FNWI)
Subjects: surveys, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), radio continuum: general, FOS: Physical sciences, Astronomy and Astrophysics, astronomical databases: miscellaneous, Astrophysics - Instrumentation and Methods for Astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), Astrophysics - Astrophysics of Galaxies, catalogs
Abstract: Full list of authors: Kutkin, A. M.; Oosterloo, T. A.; Morganti, R.; Adams, E. A. K.; Mancini, M.; Adebahr, B.; de Blok, W. J. G.; Denes, H.; Hess, K. M.; van der Hulst, J. M.; Lucero, D. M.; Moss, V. A.; Berger, A.; van den Brink, R.; van Cappellen, W. A.; Connor, L.; Damstra, S.; Loose, G. M.; van Leeuwen, J.; Maan, Y.; Mika, A.; Norden, M. J.; Offringa, A. R.; Oostrum, L. C.; van der Schuur, D.; Vohl, D.; Wijnholds, S. J.; Ziemke, J.--This is an Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited., The first data release from Apertif survey contains 3074 radio continuum images, covering a thousand square degrees of the sky. The observations were performed between August 2019 and July 2020. The continuum images were produced at a central frequency 1355 MHz, with a bandwidth of ~150 MHz and angular resolution of up to 10″. In this work, we introduce and apply a new method to obtain a primary beam model based on a machine-learning approach, namely, Gaussian process regression. The primary beam models obtained with this method have been published, along with the data products for the first Apertif data release. We applied the method to the continuum images, carried out a mosaicking process on their basis, and extracted the source catalog. The catalog contains 249672 radio sources, many of which have been detected for the first time at these frequencies. We cross-matched the coordinates with the NVSS, LOFAR/DR1/value-added, and LOFAR/DR2 catalogs – resulting in 44523, 22825, and 152824 common sources, respectively. The first sample provides a unique opportunity for detecting long-term transient sources, which have significantly changed their flux density over the past 25 yr. A combination of the second and the third samples provides valuable information on the spectral properties of the sources in addition to redshift estimates. © A. M. Kutkin et al. 2022., This work makes use of data from the Apertif system installed at the Westerbork Synthesis Radio Telescope owned by ASTRON. ASTRON, the Netherlands Institute for Radio Astronomy, is an institute of the Dutch Science Organisation (De Nederlandse Organisatie voor Wetenschappelijk Onderzoek, NWO). Apertif was partly financed by the NWO Groot projects Apertif (175.010.2005.015) and Apropos (175.010.2009.012). This research made use of Python programming language with its standard and external libraries/packages including numpy (Harris et al. 2020), scipy (Virtanen et al. 2020), scikit-learn (Pedregosa et al. 2011), matplotlib (Hunter 2007), pandas (McKinney 2010) etc. This research made use of Astropy, (http://www.astropy.org) a community-developed core Python package for Astronomy (Astropy Collaboration 2013, Astropy Collaboration 2018). The radio_beam and reproject python packages are used for manipulations with restoring beam and reprojecting/mosaicking of the images. This research has made use of “Aladin sky atlas” developed at CDS, Strasbourg Observatory, France (Bonnarel et al. 2000; Boch & Fernique 2014). E.A.K.A. is supported by the WISE research programme, which is financed by the Netherlands Organization for Scientific Research (NWO) B.A. acknowledges funding from the German Science Foundation DFG, within the Collaborative Research Center SFB1491 “Cosmic Interacting Matters – From Source to Signal”. T.A.O. acknowledges funding from NWO via grant TOP1EW.14.105. K.M.H. acknowledges financial support from the State Agency for Research of the Spanish Ministry of Science, Innovation and Universities through the “Center of Excellence Severo Ochoa” awarded to the Instituto de Astrofísica de Andalucía (SEV-2017-0709), from the coordination of the participation in SKA-SPAIN, funded by the Ministry of Science and Innovation (MCIN). K.M.H. and J.M.vdH. acknowledge funding from the Europeaní Research Council under the European Union’s Seventh Framework Programme (FP/2007–2013)/ERC Grant Agreement No. 291531 (‘HIStoryNU’). L.C. and L.C.O. acknowledge funding from the European Research Council under the European Union’s Seventh Framework Programme (FP/2007–2013)/ERC Grant Agreement No. 617199. J.vL. acknowledges funding from Vici research programme “ARGO” with project number 639.043.815, financed by the Dutch Research Council (NWO). D.V. acknowledges support from the Netherlands eScience Center (NLeSC) under grant ASDI.15.406.
Published: 2022

3. First release of Apertif imaging survey data

Author: E. A. K. Adams, B. Adebahr, W. J. G. de Blok, H. Dénes, K. M. Hess, J. M. van der Hulst, A. Kutkin, D. M. Lucero, R. Morganti, V. A. Moss, T. A. Oosterloo, E. Orrú, R. Schulz, A. S. van Amesfoort, A. Berger, O. M. Boersma, M. Bouwhuis, R. van den Brink, W. A. van Cappellen, L. Connor, A. H. W. M. Coolen, S. Damstra, G. N. J. van Diepen, T. J. Dijkema, N. Ebbendorf, Y. G. Grange, R. de Goei, A. W. Gunst, H. A. Holties, B. Hut, M. V. Ivashina, G. I. G. Józsa, J. van Leeuwen, G. M. Loose, Y. Maan, M. Mancini, Á. Mika, H. Mulder, M. J. Norden, A. R. Offringa, L. C. Oostrum, I. Pastor-Marazuela, D. J. Pisano, A. A. Ponomareva, J. W. Romein, M. Ruiter, A. P. Schoenmakers, D. van der Schuur, J. J. Sluman, R. Smits, K. J. C. Stuurwold, J. Verstappen, N. P. E. Vilchez, D. Vohl, K. J. Wierenga, S. J. Wijnholds, E. E. M. Woestenburg, A. W. Zanting, J. Ziemke, Astronomy, Kapteyn Astronomical Institute, Ministerio de Ciencia e Innovación (España), European Commission, European Research Council, and German Research Foundation
Subjects: Galaxies: ISM, Radio lines: galaxies, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), Polarization, FOS: Physical sciences, Astronomy and Astrophysics, Surveys, Astrophysics - Instrumentation and Methods for Astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), Astrophysics - Astrophysics of Galaxies, Radio continuum: galaxies
Abstract: Full list of authors: Adams, E. A. K.; Adebahr, B.; de Blok, W. J. G.; Denes, H.; Hess, K. M.; van der Hulst, J. M.; Kutkin, A.; Lucero, D. M.; Morganti, R.; Moss, V. A.; Oosterloo, T. A.; Orru, E.; Schulz, R.; van Amesfoort, A. S.; Berger, A.; Boersma, O. M.; Bouwhuis, M.; van den Brink, R.; van Cappellen, W. A.; Connor, L.; Coolen, A. H. W. M.; Damstra, S.; van Diepen, G. N. J.; Dijkema, T. J.; Ebbendorf, N.; Grange, Y. G.; de Goei, R.; Gunst, A. W.; Holties, H. A.; Hut, B.; Ivashina, M., V; Jozsa, G. I. G.; van Leeuwen, J.; Loose, G. M.; Maan, Y.; Mancini, M.; Mika, A.; Mulder, H.; Norden, M. J.; Offringa, A. R.; Oostrum, L. C.; Pastor-Marazuela, I; Pisano, D. J.; Ponomareva, A. A.; Romein, J. W.; Ruiter, M.; Schoenmakers, A. P.; van der Schuur, D.; Sluman, J. J.; Smits, R.; Stuurwold, K. J. C.; Verstappen, J.; Vilchez, N. P. E.; Vohl, D.; Wierenga, K. J.; Wijnholds, S. J.; Woestenburg, E. E. M.; Zanting, A. W.; Ziemke, J.--Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited., Context. Apertif is a phased-array feed system for the Westerbork Synthesis Radio Telescope, providing forty instantaneous beams over 300 MHz of bandwidth. A dedicated survey program utilizing this upgrade started on 1 July 2019, with the last observations taken on 28 February 2022. The imaging survey component provides radio continuum, polarization, and spectral line data. Aims. Public release of data is critical for maximizing the legacy of a survey. Toward that end, we describe the release of data products from the first year of survey operations, through 30 June 2020. In particular, we focus on defining quality control metrics for the processed data products. Methods. The Apertif imaging pipeline, Apercal, automatically produces non-primary beam corrected continuum images, polarization images and cubes, and uncleaned spectral line and dirty beam cubes for each beam of an Apertif imaging observation. For this release, processed data products are considered on a beam-by-beam basis within an observation. We validate the continuum images by using metrics that identify deviations from Gaussian noise in the residual images. If the continuum image passes validation, we release all processed data products for a given beam. We apply further validation to the polarization and line data products and provide flags indicating the quality of those data products. Results. We release all raw observational data from the first year of survey observations, for a total of 221 observations of 160 independent target fields, covering approximately one thousand square degrees of sky. Images and cubes are released on a per beam basis, and 3374 beams (of 7640 considered) are released. The median noise in the continuum images is 41.4 uJy beam−1, with a slightly lower median noise of 36.9 uJy beam−1 in the Stokes V polarization image. The median angular resolution is 11.6″/sin δ. The median noise for all line cubes, with a spectral resolution of 36.6 kHz, is 1.6 mJy beam−1, corresponding to a 3-σ H I column density sensitivity of 1.8 × 1020 atoms cm−2 over 20 km s−1 (for a median angular resolution of 24″ × 15″). Line cubes at lower frequency have slightly higher noise values, consistent with the global RFI environment and overall Apertif system performance. We also provide primary beam images for each individual Apertif compound beam. The data are made accessible using a Virtual Observatory interface and can be queried using a variety of standard tools. © E. A. K. Adams et al. 2022., This work makes use of data from the Apertif system installed at the Westerbork Synthesis Radio Telescope owned by ASTRON. ASTRON, the Netherlands Institute for Radio Astronomy, is an institute of the Dutch Research Council (“De Nederlandse Organisatie voor Wetenschappelijk Onderzoek, NWO). Apertif was partly financed by the NWO Groot projects Apertif (175.010.2005.015) and Apropos (175.010.2009.012). This work was partly supported by funding from the European Research Council under the European Union’s Seventh Frame-work Programme (FP/2007-2013), through ERC Grant Agreement No. 291531 (‘HIStoryNU’, PI: JMvdH) and ERC Advanced Grant RADIOLIFE-320745 (PI: RM), in addition to funding from NWO via grant TOP1EW.14.105 (PI: TAO). E.A.K.A. is supported by the WISE research programme, which is financed by NWO. B.A. acknowledges funding from the German Science Foundation DFG, within the Collaborative Research Center SFB1491 “Cosmic Interacting Matters - From Source to Signal”. KMH acknowledges financial support from the State Agency for Research of the Spanish Ministry of Science, Innovation and Universities through the “Center of Excellence Severo Ochoa” awarded to the Instituto de Astrofísica de Andalucía (SEV-2017-0709), from the coordination of the participation in SKA-SPAIN, funded by the Ministry of Science and Innovation (MCIN). OMB and JvL acknowledge funding from NWO under the Vici research program “ARGO” with project number 639.043.815. Y.M., L.C.O., R.S. and J.vL. acknowledge funding from the European Research Council under the European Union’s Seventh Framework Programme (FP/2007-2013)/ERC Grant Agreement No. 617199 (“ALERT”). IPM acknowledges funding from the Netherlands Research School for Astronomy (grant no. NOVA5-NW3-10.3.5.14). A.A.P. acknowledges support of the STFC consolidated grant ST/S000488/1. DV acknowledges support from the Netherlands eScience Center (NLeSC) under grant ASDI.15.406. This research has made use of NASA’s Astrophysics Data System Bibliographic Services and Astropy, (http://www.astropy.org) a community-developed core Python package for Astronomy (Astropy Collaboration 2013, 2018).
Published: 2022

4. The Apertif science verification campaign

Author: B. Adebahr, A. Berger, E. A. K. Adams, K. M. Hess, W. J. G. de Blok, H. Dénes, V. A. Moss, R. Schulz, J. M. van der Hulst, L. Connor, S. Damstra, B. Hut, M. V. Ivashina, G. M. Loose, Y. Maan, A. Mika, H. Mulder, M. J. Norden, L. C. Oostrum, E. Orrú, M. Ruiter, R. Smits, W. A. van Cappellen, J. van Leeuwen, N. J. Vermaas, D. Voh, J. Ziemke, Astronomy, Kapteyn Astronomical Institute, High Energy Astrophys. & Astropart. Phys (API, FNWI), Ministerio de Ciencia e Innovación (España), European Research Council, and German Research Foundation
Subjects: polarization, Cosmology and Nongalactic Astrophysics (astro-ph.CO), galaxies: active, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, methods: data analysis, Astrophysics - Astrophysics of Galaxies, surveys, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), galaxies: magnetic fields, Astrophysics - Instrumentation and Methods for Astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), Astrophysics::Galaxy Astrophysics, Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract: Context. The characteristics of the polarised radio sky are a key ingredient in constraining evolutionary models of magnetic fields in the Universe and their role in feedback processes. The origin of the polarised emission and the characteristics of the intergalactic medium on the line of sight can be investigated using large samples of polarised sources. Ancillary infrared (IR) and optical data can be used to study the nature of the emitting objects. Aims. We analyse five early science datasets from the APERture Tile in Focus (Apertif) phased array feed system to verify the polarisation capabilities of Apertif in view of future larger data releases. We aim to characterise the source population of the polarised sky in the L-Band using polarised source information in combination with IR and optical data. Methods. We use automatic routines to generate full field-of-view Q- and U-cubes and perform rotation measure (RM)-Synthesis, source finding, and cross-matching with published radio, optical, and IR data to generate polarised source catalogues. All sources were inspected individually by eye for verification of their IR and optical counterparts. Spectral energy distribution (SED)-fitting routines were used to determine photometric redshifts, star-formation rates, and galaxy masses. IR colour information was used to classify sources as active galactic nuclei (AGN) or star-forming-dominated and early- or late-type. Results. We surveyed an area of 56 deg2 and detected 1357 polarised source components in 1170 sources. The fraction of polarised sources is 10.57% with a median fractional polarisation of 4.70 ± 0.14%. We confirmed the reliability of the Apertif measurements by comparing them with polarised cross-identified NVSS sources. Average RMs of the individual fields lie within the error of the best Milky Way foreground measurements. All of our polarised sources were found to be dominated by AGN activity in the radio regime with most of them being radio-loud (79%) and of the Fanaroff-Riley (FR)II class (87%). The host galaxies of our polarised source sample are dominated by intermediate disc and star-forming disc galaxies. The contribution of star formation to the radio emission is on the order of a few percent for ≈10% of the polarised sources while for ≈90% it is completely dominated by the AGN. We do not see any change in fractional polarisation for different star-formation rates of the AGN host galaxies. Conclusions. The Apertif system is suitable for large-area high-sensitivity polarised sky surveys. The data products of the polarisation analysis pipeline can be used to investigate the Milky Way magnetic field on projected scales of several arcminutes as well as the origin of the polarised emission in AGN and the properties of their host galaxies. © ESO 2022., This research made use of Montage. It is funded by the National Science Foundation under Grant Number ACI-1440620, and was previously funded by the National Aeronautics and Space Administration’s Earth Science Technology Office, Computation Technologies Project, under Cooperative Agreement Number NCC5-626 between NASA and the California Institute of Technology. The Montage distribution includes an adaptation of the MOPEX algorithm developed at the Spitzer Science Center. BA and AB acknowledge funding from the German Science Foundation DFG, within the Collaborative Research Center SFB1491 “Cosmic Interacting Matters - From Source to Signal”. EAKA is supported by the WISE research programme, which is financed by the Dutch Research Council (NWO). K.M.H. acknowledges funding from the State Agency for Research of the Spanish Ministry of Science, Innovation and Universities through the “Center of Excellence Severo Ochoa” awarded to the Instituto de Astrofísica de Andalucía (SEV-2017-0709); from grant RTI2018-096228-B-C31 (Ministry of Science, Innovation and Universities/State Agency for Research/European Regional Development Funds, European Union); and from the coordination of the participation in SKA-SPAIN, funded by the Ministry of Science and innovation (MICIN). J.M.vdH. and K.M.H. acknowledge funding from the European Research Council under the European Union’s Seventh Framework Programme (FP/2007-2013)/ERC Grant Agreement No. 291531 (‘HIStoryNU’). J.vL. acknowledges funding from the European Research Council under the European Union’s Seventh Framework Programme (FP/2007–2013)/ERC Grant Agreement no. 617199 (‘ALERT’), and from Vici research programme ‘ARGO’ with project number 639.043.815, financed by the Dutch Research Council (NWO). DV acknowledges support from the Netherlands eScience Center (NLeSC) under grant ASDI.15.406. RS acknowledges funding from the European Research Council under the European Union’s Seventh Framework Programme (FP/2007–2013)/ERC Grant Agreement No. 617199. LCO acknowledges funding from the European Research Council under the European Union’s Seventh Framework Programme (FP/2007–2013)/ERC Grant Agreement No. 617199.
Published: 2022

5. The LOFAR LBA Sky Survey

Author: F. de Gasperin, H. W. Edler, W. L. Williams, J. R. Callingham, B. Asabere, M. Brüggen, G. Brunetti, T. J. Dijkema, M. J. Hardcastle, M. Iacobelli, A. Offringa, M. J. Norden, H. J. A. Röttgering, T. Shimwell, R. J. van Weeren, C. Tasse, D. J. Bomans, A. Bonafede, A. Botteon, R. Cassano, K. T. Chyży, V. Cuciti, K. L. Emig, M. Kadler, G. Miley, B. Mingo, M. S. S. L. Oei, I. Prandoni, D. J. Schwarz, and P. Zarka
Subjects: surveys, general, Space and Planetary Science, FOS: Physical sciences, processing, Astronomy and Astrophysics, image, Astrophysics - Instrumentation and Methods for Astrophysics, techniques, Instrumentation and Methods for Astrophysics (astro-ph.IM), catalogs, radio continuum
Abstract: The Low Frequency Array (LOFAR) is the only existing radio interferometer able to observe at ultra-low frequencies (, 20 pages, 22 figures, images and catalogues available at https://www.lofar-surveys.org/lolss.html
Published: 2023

6. Apertif: Phased array feeds for the Westerbork Synthesis Radio Telescope. System overview and performance characteristics

Author: W. A. van Cappellen, T. A. Oosterloo, M. A. W. Verheijen, E. A. K. Adams, B. Adebahr, R. Braun, K. M. Hess, H. Holties, J. M. van der Hulst, B. Hut, E. Kooistra, J. van Leeuwen, G. M. Loose, R. Morganti, V. A. Moss, E. Orrú, M. Ruiter, A. P. Schoenmakers, N. J. Vermaas, S. J. Wijnholds, A. S. van Amesfoort, M. J. Arts, J. J. Attema, L. Bakker, C. G. Bassa, J. E. Bast, P. Benthem, R. Beukema, R. Blaauw, W. J. G. de Blok, M. Bouwhuis, R. H. van den Brink, L. Connor, A. H. W. M. Coolen, S. Damstra, G. N. J. van Diepen, R. de Goei, H. Dénes, M. Drost, N. Ebbendorf, B. S. Frank, D. W. Gardenier, M. Gerbers, Y. G. Grange, T. Grit, A. W. Gunst, N. Gupta, M. V. Ivashina, G. I. G. Józsa, G. H. Janssen, A. Koster, G. H. Kruithof, S. J. Kuindersma, A. Kutkin, D. M. Lucero, Y. Maan, F. M. Maccagni, J. van der Marel, A. Mika, J. Morawietz, H. Mulder, E. Mulder, M. J. Norden, A. R. Offringa, L. C. Oostrum, R. E. Overeem, Z. Paragi, H. J. Pepping, E. Petroff, D. J. Pisano, A. G. Polatidis, P. Prasad, J. P. R. de Reijer, J. W. Romein, J. Schaap, G. W. Schoonderbeek, R. Schulz, D. van der Schuur, A. Sclocco, J. J. Sluman, R. Smits, B. W. Stappers, S. M. Straal, K. J. C. Stuurwold, J. Verstappen, D. Vohl, K. J. Wierenga, E. E. M. Woestenburg, A. W. Zanting, J. Ziemke, Astronomy, and Kapteyn Astronomical Institute
Subjects: Radio telescope, Physics, Space and Planetary Science, Phased array, Instrumentation: interferometers, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy, Astronomy and Astrophysics, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Surveys, Telescopes
Abstract: We describe the APERture Tile In Focus (Apertif) system, a phased array feed (PAF) upgrade of the Westerbork Synthesis Radio Telescope that transforms this telescope into a high-sensitivity, wide-field-of-view L-band imaging and transient survey instrument. Using novel PAF technology, up to 40 partially overlapping beams are formed on the sky simultaneously, significantly increasing the survey speed of the telescope. With this upgraded instrument, an imaging survey covering an area of 2300 deg2 is being performed that will deliver both continuum and spectral line datasets, of which the first data have been publicly released. In addition, a time domain transient and pulsar survey covering 15 000 deg2 is in progress. An overview of the Apertif science drivers, hardware, and software of the upgraded telescope is presented, along with its key performance characteristics.
Published: 2022

7. Sub-arcsecond imaging with the International LOFAR Telescope II. Completion of the LOFAR Long-Baseline Calibrator Survey

Author: G. K. Miley, Annalisa Bonafede, M. P. van Haarlem, Jochen Eislöffel, John McKean, P. C. G. van Dijk, M. A. Garrett, B. Ciardi, R. Blaauw, E. Jütte, Harvey Butcher, O. Wucknitz, Luitje Koopmans, Oleg Smirnov, M. Pandey-Pommier, Pietro Zucca, Joseph R. Callingham, S. Mooney, R. J. van Weeren, A. Nelles, Antonia Rowlinson, W. Reich, Heino Falcke, S. Duscha, Rajan Chhetri, Emanuela Orrú, G. Mann, Dominik J. Schwarz, Michiel A. Brentjens, P. Zarka, M. Ruiter, Hanna Rothkaehl, Kaspars Prūsis, Ralph A. M. J. Wijers, S. Badole, Jean-Mathias Griessmeier, P. Maat, Neal Jackson, Marco Iacobelli, Jeremy J. Harwood, Andrzej Krankowski, M. J. Norden, Vishambhar Pandey, A. J. van der Horst, John Morgan, F. Sweijen, Adam Deller, George Heald, S. Damstra, Martin J. Hardcastle, Mark J. Bentum, Ashish Asgekar, Leah K. Morabito, A. W. Gunst, M. Tagger, A. Shulevski, C. Vocks, A. Drabent, Javier Moldon, A. H. W. M. Coolen, M. Paas, Atvars Nikolajevs, W. N. Brouw, J. Sluman, Roberto Pizzo, Marcus Brüggen, Henk Mulder, Matthias Hoeft, F. de Gasperin, I. M. Avruch, J. A. Zensus, Arthur Corstanje, Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Unité Scientifique de la Station de Nançay (USN), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics (LESIA), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), European Commission, Ministerio de Ciencia e Innovación (España), Netherlands Organization for Scientific Research, UK Research and Innovation, Chinese Academy of Sciences, High Energy Astrophys. & Astropart. Phys (API, FNWI), Kapteyn Astronomical Institute, Center for Wireless Technology Eindhoven, and EM for Radio Science Lab
Subjects: active -Radio continuum, active [Galaxies], Radio galaxy, galaxies -Atmospheric physics, Astronomy, media_common.quotation_subject, FOS: Physical sciences, Flux, Murchison Widefield Array, ionosphere, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Surveys, Interplanetary scintillation, Instrumentation and Methods for Astrophysics (astro-ph.IM), Instrumentation, Remote sensing, media_common, Physics, Spectral index, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], Radio lines: galaxies, Astrophysics::Instrumentation and Methods for Astrophysics, interferometers [Instrumentation], Astronomy and Astrophysics, Quasar, LOFAR, Galaxies: active, interferometers -Techniques, Astrophysics - Astrophysics of Galaxies, galaxies [Radio lines], Space and Planetary Science, Sky, [SDU]Sciences of the Universe [physics], Instrumentation: interferometers, Astrophysics of Galaxies (astro-ph.GA), Techniques: interferometric, interferometric [Techniques], interferometric -Surveys -Galaxies, Astrophysics - Instrumentation and Methods for Astrophysics
Abstract: Full list of authors: Jackson, N.; Badole, S.; Morgan, J.; Chhetri, R.; Prūsis, K.; Nikolajevs, A.; Morabito, L.; Brentjens, M.; Sweijen, F.; Iacobelli, M.; Orrù, E.; Sluman, J.; Blaauw, R.; Mulder, H.; van Dijk, P.; Mooney, S.; Deller, A.; Moldon, J.; Callingham, J. R.; Harwood, J.; Hardcastle, M.; Heald, G.; Drabent, A.; McKean, J. P.; Asgekar, A.; Avruch, I. M.; Bentum, M. J.; Bonafede, A.; Brouw, W. N.; Brüggen, M.; Butcher, H. R.; Ciardi, B.; Coolen, A.; Corstanje, A.; Damstra, S.; Duscha, S.; Eislöffel, J.; Falcke, H.; Garrett, M.; de Gasperin, F.; Griessmeier, J. -M.; Gunst, A. W.; van Haarlem, M. P.; Hoeft, M.; van der Horst, A. J.; Jütte, E.; Koopmans, L. V. E.; Krankowski, A.; Maat, P.; Mann, G.; Miley, G. K.; Nelles, A.; Norden, M.; Paas, M.; Pandey, V. N.; Pandey-Pommier, M.; Pizzo, R. F.; Reich, W.; Rothkaehl, H.; Rowlinson, A.; Ruiter, M.; Shulevski, A.; Schwarz, D. J.; Smirnov, O.; Tagger, M.; Vocks, C.; van Weeren, R. J.; Wijers, R.; Wucknitz, O.; Zarka, P.; Zensus, J. A.; Zucca, P., The Low-Frequency Array (LOFAR) Long-Baseline Calibrator Survey (LBCS) was conducted between 2014 and 2019 in order to obtain a set of suitable calibrators for the LOFAR array. In this paper, we present the complete survey, building on the preliminary analysis published in 2016 which covered approximately half the survey area. The final catalogue consists of 30 006 observations of 24 713 sources in the northern sky, selected for a combination of high low-frequency radio flux density and flat spectral index using existing surveys (WENSS, NVSS, VLSS, and MSSS). Approximately one calibrator per square degree, suitable for calibration of ≥200 km baselines is identified by the detection of compact flux density, for declinations north of 30° and away from the Galactic plane, with a considerably lower density south of this point due to relative difficulty in selecting flat-spectrum candidate sources in this area of the sky. The catalogue contains indicators of degree of correlated flux on baselines between the Dutch core and each of the international stations, involving a maximum baseline length of nearly 2000 km, for all of the observations. Use of the VLBA calibrator list, together with statistical arguments by comparison with flux densities from lower-resolution catalogues, allow us to establish a rough flux density scale for the LBCS observations, so that LBCS statistics can be used to estimate compact flux densities on scales between 300 mas and 2′′, for sources observed in the survey. The survey is used to estimate the phase coherence time of the ionosphere for the LOFAR international baselines, with median phase coherence times of about 2 min varying by a few tens of percent between theshortest and longest baselines. The LBCS can be used to assess the structures of point sources in lower-resolution surveys, with significant reductions in the degree of coherence in these sources on scales between 2′′ and 300 mas. The LBCS survey sources show a greater incidence of compact flux density in quasars than in radio galaxies, consistent with unified schemes of radio sources. Comparison with samples of sources from interplanetary scintillation (IPS) studies with the Murchison Widefield Array shows consistent patterns of detection of compact structure in sources observed both interferometrically with LOFAR and using IPS. © ESO 2022., Support for the operation of the MWA is provided by the Australian Government (NCRIS), under a contract to Curtin University administered by Astronomy Australia Limited. We acknowledge the Pawsey Supercomputing Centre which is supported by the Western Australian and Australian Governments. A.D. acknowledges support by the BMBF Verbundforschung under the grant 052020. L.K.M. is grateful for support from the UKRI Future Leaders Fellowship (grant MR/T042842/1). J. Moldón acknowledges financial support from the State Agency for Research of the Spanish MCIU through the “Center of Excellence Severo Ochoa” award to the Instituto de Astrofísica de Andalucía (SEV-2017-0709) and from the grant RTI2018-096228-B-C31 (MICIU/FEDER, EU). J.P.M. acknowledges support from the Netherlands Organization for Scientific Research (NWO, project number 629.001.023) and the Chinese Academy of Sciences (CAS, project number 114A11KYSB20170054).
Published: 2022

8. Apertif: lessons learned operating a Phased Array Feed array

Author: Henk Mulder, S. van der Tol, M. J. Norden, Emanuela Orrú, V. A. Moss, L. C. Oostrum, A. H. W. M. Coolen, A. P. Schoenmakers, H. Holties, J. van Leeuwen, M. Bouwhuis, N. Veermas, and Elizabeth A. K. Adams
Subjects: Radio telescope, Phased array feed, business.industry, Computer science, Phased array, Systems engineering, Signal processing algorithms, business, Automation, Radio astronomy
Abstract: Apertif is the phased array feeds (PAFs) system operational on the Westerbork Synthesis Radio Telescope. This paper will cover various aspects of the system describing how the instrument is operated on a daily basis. Focus will be given to the use of new technology adopted for the hardware monitoring, automation of operational routines, calibration of the instrument and the results and lessons learned by operating it.
Published: 2021

9. Chromatic periodic activity down to 120 megahertz in a fast radio burst

Author: H. Dénes, S. M. Straal, Tom Oosterloo, Thijs van der Hulst, A. Kutkin, Joeri van Leeuwen, Dany Vohl, Henk Mulder, Jisk Attema, W. J. G. de Blok, M. J. Norden, Alessio Sclocco, Oliver M. Boersma, Á. Mika, S. Damstra, Sander ter Veen, Stefan J. Wijnholds, Kelley M. Hess, Emanuela Orrú, Daniel van der Schuur, Elizabeth A. K. Adams, E. Kooistra, Liam Connor, A. H. W. M. Coolen, Yogesh Maan, R. Smits, M. Ruiter, L. C. Oostrum, D. M. Lucero, Inés Pastor-Marazuela, B. Hut, Emily Petroff, V. Marianna Ivashina, A. V. Bilous, B. Adebahr, G. Marcel Loose, Vanessa A. Moss, High Energy Astrophys. & Astropart. Phys (API, FNWI), API Other Research (FNWI), Astronomy, and Kapteyn Astronomical Institute
Subjects: Physics, High Energy Astrophysical Phenomena (astro-ph.HE), Brightness, Multidisciplinary, High-energy astronomy, Fast radio burst, media_common.quotation_subject, FOS: Physical sciences, Astrophysics, Radiation, Wavelength, Sky, Chromatic scale, Astrophysics - High Energy Astrophysical Phenomena, media_common, Time domain astronomy
Abstract: Fast radio bursts (FRBs) are extragalactic astrophysical transients whose brightness requires emitters that are highly energetic, yet compact enough to produce the short, millisecond-duration bursts. FRBs have thus far been detected between 300 MHz and 8 GHz, but lower-frequency emission has remained elusive. A subset of FRBs is known to repeat, and one of those sources, FRB 20180916B, does so with a 16.3 day activity period. Using simultaneous Apertif and LOFAR data, we show that FRB 20180916B emits down to 120 MHz, and that its activity window is both narrower and earlier at higher frequencies. Binary wind interaction models predict a narrower periodic activity window at lower frequencies, which is the opposite of our observations. Our detections establish that low-frequency FRB emission can escape the local medium. For bursts of the same fluence, FRB 20180916B is more active below 200 MHz than at 1.4 GHz. Combining our results with previous upper-limits on the all-sky FRB rate at 150 MHz, we find that there are 3-450 FRBs/sky/day above 50 Jy ms at 90% confidence. We are able to rule out the scenario in which companion winds cause FRB periodicity. We also demonstrate that some FRBs live in clean environments that do not absorb or scatter low-frequency radiation., Comment: 50 pages, 14 figures, 3 tables, submitted
Published: 2021

10. Apertif view of the OH megamaser IRAS 10597+5926

Author: M. J. Norden, A. Kutkin, Dany Vohl, Stefan J. Wijnholds, A. H. W. M. Coolen, R. Schulz, Á. Mika, L. C. Oostrum, S. Damstra, Henk Mulder, Tom Oosterloo, D. M. Lucero, H. Roberts, Jeremy Darling, Yogesh Maan, Joeri van Leeuwen, J. Ziemke, J. M. van der Hulst, M. Ruiter, W. J. G. de Blok, Kelley M. Hess, N. J. Vermaas, B. Adebahr, G. Marcel Loose, E. A. K. Adams, V. A. Moss, Raffaella Morganti, Marianna Ivashina, H. Dénes, API Other Research (FNWI), High Energy Astrophys. & Astropart. Phys (API, FNWI), Astronomy, and Kapteyn Astronomical Institute
Subjects: Infrared, Megamaser, FOS: Physical sciences, galaxies: starburst, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, 01 natural sciences, galaxies: groups: individual: IRAS 10597+5926, Luminosity, law.invention, masers, law, 0103 physical sciences, galaxies: interactions, Astrophysics::Solar and Stellar Astrophysics, Maser, 010306 general physics, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, radio lines: galaxies, Luminous infrared galaxy, Physics, Star formation, Astronomy and Astrophysics, Astrophysics - Astrophysics of Galaxies, Galaxy, 13. Climate action, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), Satellite, galaxies: ISM
Abstract: We present the serendipitous detection of the two main OH maser lines at 1667 and 1665 MHz associated with IRAS 10597+5926 at z = 0.19612 in the untargeted Apertif Wide-area Extragalactic Survey (AWES), and the subsequent measurement of the OH 1612 MHz satellite line in the same source. With a total OH luminosity of log(L/L_Sun) = 3.90 +/- 0.03, IRAS 10597+5926 is the fourth brightest OH megamaser (OHM) known. We measure a lower limit for the 1667/1612 ratio of R_1612 > 45.9 which is the highest limiting ratio measured for the 1612 MHz OH satellite line to date. OH satellite line measurements provide a potentially valuable constraint by which to compare detailed models of OH maser pumping mechanisms. Optical imaging shows the galaxy is likely a late-stage merger. Based on published infrared and far ultraviolet fluxes, we find that the galaxy is an ultra luminous infrared galaxy (ULIRG) with log(L_TIR/L_Sun) = 12.24, undergoing a star burst with an estimated star formation rate of 179 +/- 40 M_Sun/yr. These host galaxy properties are consistent with the physical conditions responsible for very bright OHM emission. Finally, we provide an update on the predicted number of OH masers that may be found in AWES, and estimate the total number of OH masers that will be detected in each of the individual main and satellite OH 18 cm lines., 9 pages, 4 figures. Accepted for publication in A&A
Published: 2021

11. The LOFAR LBA Sky Survey

Author: F. de Gasperin, W. L. Williams, P. Best, M. Brüggen, G. Brunetti, V. Cuciti, T. J. Dijkema, M. J. Hardcastle, M. J. Norden, A. Offringa, T. Shimwell, R. van Weeren, D. Bomans, A. Bonafede, A. Botteon, J. R. Callingham, R. Cassano, K. T. Chyży, K. L. Emig, H. Edler, M. Haverkorn, G. Heald, V. Heesen, M. Iacobelli, H. T. Intema, M. Kadler, K. Małek, M. Mevius, G. Miley, B. Mingo, L. K. Morabito
Published: 2021
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12. The best of both worlds: Combining LOFAR and Apertif to derive resolved radio spectral index images

Author: Emanuela Orru, D. M. Lucero, H. J. A. Röttgering, M. J. Norden, G. M. Loose, A. M. Kutkin, Marisa Brienza, Tom Oosterloo, M. Ruiter, J. van Leeuwen, Dany Vohl, S. Damstra, Vanessa A. Moss, F. M. Maccagni, G. M. van Diepen, N. J. Vermaas, B. Hut, R. Kondapally, J. Ziemke, B. Adebahr, Martin J. Hardcastle, J. M. van der Hulst, R. I. J. Mostert, A. H. W. M. Coolen, N. Jurlin, Timothy W. Shimwell, W. J. G. de Blok, R. Morganti, Kelley M. Hess, Robert Schulz, Beatriz Mingo, Philip Best, L. C. Oostrum, Helga Denes, Elizabeth A. K. Adams, Stanislav S. Shabala, Isabella Prandoni, F. de Gasperin, Yogesh Maan, Astronomy, Kapteyn Astronomical Institute, Morganti, R., Oosterloo, T. A., Brienza, M., Jurlin, N., Prandoni, I., Orrù, E., Shabala, S. S., Adams, E. A. K., Adebahr, B., Best, P. N., Coolen, A. H. W. M., Damstra, S., de Blok, W. J. G., de Gasperin, F., Dénes, H., Hardcastle, M., Hess, K. M., Hut, B., Kondapally, R., Kutkin, A. M., Loose, G. M., Lucero, D. M., Maan, Y., Maccagni, F. M., Mingo, B., Moss, V. A., Mostert, R. I. J., Norden, M. J., Oostrum, L. C., Röttgering, H. J. A., Ruiter, M., Shimwell, T. W., Schulz, R., Vermaas, N. J., Vohl, D., van der Hulst, J. M., van Diepen, G. M., van Leeuwen, J., Ziemke, J., API Other Research (FNWI), and High Energy Astrophys. & Astropart. Phys (API, FNWI)
Subjects: Physics, radio continuum: galaxies, Spectral index, Supermassive black hole, Active galactic nucleus, 010308 nuclear & particles physics, Radio galaxy, Astrophysics::High Energy Astrophysical Phenomena, galaxies: active, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, LOFAR, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Astrophysics - Astrophysics of Galaxies, Galaxy, Spectral line, Radio telescope, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), 0103 physical sciences, radio continuum: galaxie, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics
Abstract: Supermassive black holes at the centres of galaxies can cycle through periods of activity and quiescence. Characterising the duty cycle of active galactic nuclei is crucial for understanding the impact of the energy they release on the host galaxy. For radio AGN, this can be done by identifying dying (remnant) and restarted radio galaxies from their radio spectral properties. Using the combination of images at 1400 MHz produced by Apertif, the new phased-array feed receiver installed on the Westerbork Synthesis Radio Telescope, and images at 150 MHz provided by LOFAR, we have derived resolved spectral index images (at a resolution of ~15 arcsec) for all the sources within ~6 deg^2 area of the Lockman Hole region. We were able to select 15 extended radio sources with emission (partly or entirely) characterised by extremely steep spectral indices (steeper than 1.2). These objects represent radio sources in the remnant or the restarted phases of their life cycle. Our findings suggest this cycle to be relatively fast. They also show a variety of properties relevant for modelling the evolution of radio galaxies. For example, the restarted activity can occur while the remnant structure from a previous phase of activity is still visible. This provides constraints on the duration of the 'off' (dying) phase. In extended remnants with ultra-steep spectra at low frequencies, the activity likely stopped a few hundred megayears ago, and they correspond to the older tail of the age distribution of radio galaxies, in agreement with simulations of radio source evolution. We find remnant radio sources with a variety of structures (from double-lobed to amorphous), suggesting different types of progenitors. The present work sets the stage for exploiting low-frequency spectral index studies of extended sources by taking advantage of the large areas common to the LOFAR and the Apertif surveys., Accepted for publication in A&A. This paper is part of the 1st data release of the LoTSS Deep Fields. 17 pages, 10 figures
Published: 2021
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13. The LOFAR LBA Sky Survey. I. Survey description and preliminary data release

Author: Philip Best, R. Pizzo, Volker Heesen, Huib Intema, M. J. Norden, Cyril Tasse, Huub Röttgering, Joseph R. Callingham, Isabella Prandoni, T. J. Dijkema, Martin J. Hardcastle, Gianfranco Brunetti, R. J. van Weeren, Aleksandar Shulevski, V. Cuciti, A. Botteon, J. Sabater, Marijke Haverkorn, Leah K. Morabito, Katarzyna Małek, Matthias Kadler, Marcus Brüggen, K. L. Emig, Rossella Cassano, Marco Iacobelli, Timothy W. Shimwell, Annalisa Bonafede, Mattia Vaccari, R. Morganti, H. Edler, Beatriz Mingo, Emanuela Orru, Ph. Zarka, George K. Miley, A. R. Offringa, Dominik J. Bomans, F. de Gasperin, George Heald, M. Mevius, Wendy L. Williams, Krzysztof T. Chyzy, de Gasperin, F., Williams, W. L., Best, P., Brüggen, M., Brunetti, G., Cuciti, V., Dijkema, T. J., Hardcastle, M. J., Norden, M. J., Offringa, A., Shimwell, T., van Weeren, R., Bomans, D., Bonafede, A., Botteon, A., Callingham, J. R., Cassano, R., Chyży, K. T., Emig, K. L., Edler, H., Haverkorn, M., Heald, G., Heesen, V., Iacobelli, M., Intema, H. T., Kadler, M., Małek, K., Mevius, M., Miley, G., Mingo, B., Morabito, L. K., Sabater, J., Morganti, R., Orrú, E., Pizzo, R., Prandoni, I., Shulevski, A., Tasse, C., Vaccari, M., Zarka, P., Röttgering, H., Hamburger Sternwarte/Hamburg Observatory, Universität Hamburg (UHH), Galaxies, Etoiles, Physique, Instrumentation (GEPI), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Leiden Observatory [Leiden], Universiteit Leiden [Leiden], and Astronomy
Subjects: catalog, 010504 meteorology & atmospheric sciences, Astronomy, radio continuum: general, techniques: image processing, Astrophysics, 01 natural sciences, Low frequency arrays, Radio astronomy, 010303 astronomy & astrophysics, Spectral information, media_common, Physics, Clusters of galaxies, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], image processing [techniques], Astrophysics::Instrumentation and Methods for Astrophysics, Calibration techniques, Cosmology, general [radio continuum], Astrophysics - Instrumentation and Methods for Astrophysics, media_common.quotation_subject, FOS: Physical sciences, Context (language use), Astrophysics::Cosmology and Extragalactic Astrophysics, Population statistics, Radio telescope, surveys, 0103 physical sciences, survey, Ionosphere, Instrumentation and Methods for Astrophysics (astro-ph.IM), Astrophysics::Galaxy Astrophysics, 0105 earth and related environmental sciences, Active galactic nuclei, Ultra low frequencies, Astronomy and Astrophysics, Quasar, LOFAR, High redshift-galaxies, Galaxy, Redshift, Direction-independent, Space and Planetary Science, Sky, Magnetosphere, Antennas, catalogs, astro-ph.IM
Abstract: LOFAR is the only radio telescope that is presently capable of high-sensitivity, high-resolution (, 19 pages, 14 figures, Accepted A&A, catalogue and images on www.lofar-surveys.org
Published: 2021

14. Repeating fast radio bursts with WSRT/Apertif

Author: Alessio Sclocco, J. M. van der Hulst, G. van Diepen, Jisk Attema, W. J. G. de Blok, R. H. van den Brink, D. W. Gardenier, N. J. Vermaas, S. ter Veen, Tom Oosterloo, Stefan J. Wijnholds, M. J. Norden, Henk Mulder, Liam Connor, B. Adebahr, G. M. Loose, D. M. Lucero, B. Hut, Emily Petroff, W. A. van Cappellen, J.-P. de Reijer, J. Ziemke, L. C. Oostrum, S. Damstra, Elizabeth A. K. Adams, Dany Vohl, A. H. W. M. Coolen, R. Smits, D. van der Schuur, Emanuela Orru, Á. Mika, Yogesh Maan, J. E. Bast, M. Ruiter, Vanessa A. Moss, J. van Leeuwen, B. S. Frank, Kelley M. Hess, R. Morganti, Marianna Ivashina, E. Kooistra, Samayra Straal, J. E. Hargreaves, Astronomy, Kapteyn Astronomical Institute, High Energy Astrophys. & Astropart. Phys (API, FNWI), and API Other Research (FNWI)
Subjects: stars, DEEP, media_common.quotation_subject, FOS: Physical sciences, Context (language use), Astrophysics, 01 natural sciences, radio continuum, Radio telescope, SEARCHES, neutron, Pulsar, GIANT PULSES, 0103 physical sciences, REPETITION, 010306 general physics, 010303 astronomy & astrophysics, media_common, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, Spectral index, Astronomy and Astrophysics, Position angle, Stars, Space and Planetary Science, Sky, general, pulsars, Astrophysics - High Energy Astrophysical Phenomena, EMISSION, Energy (signal processing)
Abstract: Repeating fast radio bursts (FRBs) present excellent opportunities to identify FRB progenitors and host environments, as well as decipher the underlying emission mechanism. Detailed studies of repeating FRBs might also hold clues to the origin of FRBs as a population. We aim to detect the first two repeating FRBs: FRB 121102 (R1) and FRB 180814.J0422+73 (R2), and characterise their repeat statistics. We also want to significantly improve the sky localisation of R2. We use the Westerbork Synthesis Radio Telescope to conduct extensive follow-up of these two repeating FRBs. The new phased-array feed system, Apertif, allows covering the entire sky position uncertainty of R2 with fine spatial resolution in one pointing. We characterise the energy distribution and the clustering of detected R1 bursts. We detected 30 bursts from R1. Our measurements indicate a dispersion measure of 563.5(2) pc cm$^{-3}$, suggesting a significant increase in DM over the past few years. We place an upper limit of 8% on the linear polarisation fraction of the brightest burst. We did not detect any bursts from R2. A single power-law might not fit the R1 burst energy distribution across the full energy range or widely separated detections. Our observations provide improved constraints on the clustering of R1 bursts. Our stringent upper limits on the linear polarisation fraction imply a significant depolarisation, either intrinsic to the emission mechanism or caused by the intervening medium, at 1400 MHz that is not observed at higher frequencies. The non-detection of any bursts from R2 implies either a highly clustered nature of the bursts, a steep spectral index, or a combination of both. Alternatively, R2 has turned off completely, either permanently or for an extended period of time., 11 pages, 7 figures, submitted to A&A
Published: 2020

15. Cassiopeia A, Cygnus A, Taurus A, and Virgo A at ultra-low radio frequencies

Author: F. de Gasperin, J. Vink, J. P. McKean, A. Asgekar, I. Avruch, M. J. Bentum, R. Blaauw, A. Bonafede, J. W. Broderick, M. Brüggen, F. Breitling, W. N. Brouw, H. R. Butcher, B. Ciardi, V. Cuciti, M. de Vos, S. Duscha, J. Eislöffel, D. Engels, R. A. Fallows, T. M. O. Franzen, M. A. Garrett, A. W. Gunst, J. Hörandel, G. Heald, M. Hoeft, M. Iacobelli, L. V. E. Koopmans, A. Krankowski, P. Maat, G. Mann, M. Mevius, G. Miley, R. Morganti, A. Nelles, M. J. Norden, A. R. Offringa, E. Orrú, H. Paas, V. N. Pandey, M. Pandey-Pommier, R. Pekal, R. Pizzo, W. Reich, A. Rowlinson, H. J. A. Rottgering, D. J. Schwarz, A. Shulevski, O. Smirnov, C. Sobey, M. Soida, M. Steinmetz, M. Tagger, M. C. Toribio, A. van Ardenne, A. J. van der Horst, M. P. van Haarlem, R. J. van Weeren, C. Vocks, O. Wucknitz, P. Zarka, P. Zucca, Astronomy, Kapteyn Astronomical Institute, Unité Scientifique de la Station de Nançay (USN), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Université d'Orléans (UO)-Observatoire des Sciences de l'Univers en région Centre (OSUC), PSL Research University (PSL)-PSL Research University (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), PSL Research University (PSL)-PSL Research University (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), De Gasperin F., Vink J., McKean J.P., Asgekar A., Avruch I., Bentum M.J., Blaauw R., Bonafede A., Broderick J.W., Bruggen M., Breitling F., Brouw W.N., Butcher H.R., Ciardi B., Cuciti V., De Vos M., Duscha S., Eisloffel J., Engels D., Fallows R.A., Franzen T.M.O., Garrett M.A., Gunst A.W., Horandel J., Heald G., Hoeft M., Iacobelli M., Koopmans L.V.E., Krankowski A., Maat P., Mann G., Mevius M., Miley G., Morganti R., Nelles A., Norden M.J., Offringa A.R., Orru E., Paas H., Pandey V.N., Pandey-Pommier M., Pekal R., Pizzo R., Reich W., Rowlinson A., Rottgering H.J.A., Schwarz D.J., Shulevski A., Smirnov O., Sobey C., Soida M., Steinmetz M., Tagger M., Toribio M.C., Van Ardenne A., Van Der Horst A.J., Van Haarlem M.P., Van Weeren R.J., Vocks C., Wucknitz O., Zarka P., Zucca P., High Energy Astrophys. & Astropart. Phys (API, FNWI), Gravitation and Astroparticle Physics Amsterdam, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, and PSL Research University (PSL)-PSL Research University (PSL)-Centre National d’Études Spatiales [Paris] (CNES)
Subjects: Astronomy, media_common.quotation_subject, Astrophysics::High Energy Astrophysical Phenomena, radio continuum: general, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, radio continuum, law.invention, Telescope, law, 0103 physical sciences, Angular resolution, [PHYS.PHYS.PHYS-INS-DET]Physics [physics]/Physics [physics]/Instrumentation and Detectors [physics.ins-det], Surface brightness, 010306 general physics, Cygnus A, Instrumentation and Methods for Astrophysics (astro-ph.IM), 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, media_common, High Energy Astrophysical Phenomena (astro-ph.HE), [PHYS]Physics [physics], Physics, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy and Astrophysics, LOFAR, Astrophysics - Astrophysics of Galaxies, interferometric [techniques], Cassiopeia A, techniques: interferometric, 13. Climate action, Space and Planetary Science, Sky, general, Astrophysics of Galaxies (astro-ph.GA), interferometric, ddc:520, general [radio continuum], Radio frequency, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Instrumentation and Methods for Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], techniques, general [ontinuum]
Abstract: The four persistent radio sources in the northern sky with the highest flux density at metre wavelengths are Cassiopeia A, Cygnus A, Taurus A, and Virgo A; collectively they are called the A-team. Their flux densities at ultra-low frequencies (, 7 pages, 2 figures, accepted A&A, online data on A&A website
Published: 2020

16. A large light-mass component of cosmic rays at 10(17)-10(17.5) electronvolts from radio observations

Author: Vishambhar Pandey, D. D. Mulcahy, M. A. Garrett, J. van Leeuwen, Tim Hassall, Adam Deller, Harvey Butcher, D. Engels, H. Paas, John Conway, J. E. Enriquez, A. I. F. Stewart, M. Pandey-Pommier, Matthias Steinmetz, Rob Fender, B. Ciardi, M. Pietka, E. Juette, G. van Diepen, P. N. Best, M. C. Toribio, A. Horneffer, Chiara Ferrari, M. P. van Haarlem, S. Duscha, Mark J. Bentum, Stefan J. Wijnholds, Jochen Eislöffel, Sarod Yatawatta, Emanuela Orrú, M. Kuniyoshi, Michael Kramer, Anna Nelles, C. Vogt, R. J. van Weeren, Martin Bell, Maaijke Mevius, John D. Swinbank, P. Maat, Matthias Hoeft, M. J. Norden, Pim Schellart, D. McKay-Bukowski, J. A. Zensus, John McKean, Dominik J. Schwarz, Richard Fallows, Aris Karastergiou, Ph. Zarka, V. I. Kondratiev, T. N. G. Trinh, Stijn Buitink, Heino Falcke, Michael W. Wise, Jörg P. Rachen, Benjamin Stappers, Jason W. T. Hessels, J. Sluman, Gianni Bernardi, Jörg R. Hörandel, I. M. Avruch, James M. Anderson, F. de Gasperin, Frank Breitling, Roberto Pizzo, H. J. A. Röttgering, Satyendra Thoudam, G. Kuper, Olaf Wucknitz, M. Serylak, H. Munk, Wilfred Frieswijk, Ashish Asgekar, Marcus Brüggen, M. Iacobelli, Y. Tang, W. Reich, S. ter Veen, A. W. Gunst, Anna M. M. Scaife, Laura Rossetto, Ralph A. M. J. Wijers, A. G. Polatidis, Rebecca McFadden, Arthur Corstanje, Annalisa Bonafede, Christian Vocks, G. M. Loose, Sera Markoff, Jean-Mathias Grießmeier, Michel Tagger, D. Carbone, R. C. Vermeulen, T. Huege, Olaf Scholten, Oleg Smirnov, Huib Intema, Cyril Tasse, J. W. Broderick, E. de Geus, R. J. Dettmar, George Heald, W. N. Brouw, Gottfried Mann, High Energy Astrophys. & Astropart. Phys (API, FNWI), Radboud University [Nijmegen], Netherlands Institute for Radio Astronomy (ASTRON), Karlsruhe Institute of Technology (KIT), University of Groningen [Groningen], Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), Laboratoire Analyse, Géométrie et Applications (LAGA), Université Paris 8 Vincennes-Saint-Denis (UP8)-Université Paris 13 (UP13)-Institut Galilée-Centre National de la Recherche Scientifique (CNRS), Institute for Mathematics Applied to Geoscience, National Center for Atmospheric Research [Boulder] (NCAR), SRON Netherlands Institute for Space Research (SRON), Australia Telescope National Facility (ATNF), Commonwealth Scientific and Industrial Research Organisation [Canberra] (CSIRO), University of Edinburgh, Jacobs University [Bremen], Leibniz-Institut für Astrophysik Potsdam (AIP), University of Southampton, Kapteyn Astronomical Institute [Groningen], University of Amsterdam [Amsterdam] (UvA), Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, Onsala Space Observatory, Dept. of Radio and Space Science, Chalmers University of Technology, Chalmers University of Technology [Göteborg], Hamburger Sternwarte/Hamburg Observatory, Universität Hamburg (UHH), Medstar Research Institute, Astronomisches Institut der Ruhr-Universität Bochum, Ruhr-Universität Bochum [Bochum], Thüringer Landessternwarte Tautenburg (TLS), SETI Institute, Institute of Mathematical and Physical Sciences, Département de Géologie, Université de Montréal (UdeM), Leiden Observatory [Leiden], Universiteit Leiden, Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Unité Scientifique de la Station de Nançay (USN), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Jodrell Bank Centre for Astrophysics, University of Manchester [Manchester], Max-Planck-Institut für Radioastronomie (MPIFR), Oxford Astrophysics, University of Oxford, Columbia Astrophysics Laboratory (CAL), Columbia University [New York], Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Oulu, Center for Information Technology CIT, Université de Groningen, Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), National Radio Astronomy Observatory [Charlottesville] (NRAO), National Radio Astronomy Observatory (NRAO), School of Physics and Astronomy [Southampton], Interactions Son Musique Mouvement, Sciences et Technologies de la Musique et du Son (STMS), Institut de Recherche et Coordination Acoustique/Musique (IRCAM)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche et Coordination Acoustique/Musique (IRCAM)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), Rhodes University, Grahamstown, Leibniz-Institut DSMZ-Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH / Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures (DSMZ), Laboratory for Atmospheric and Space Physics [Boulder] (LASP), University of Colorado [Boulder], Université Paris-Sud - Paris 11 (UP11), SKA South Africa, Ska South Africa, Galaxies, Etoiles, Physique, Instrumentation (GEPI), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Finca El Encin, Instituto Madrileño de Investigación y Desarrollo Rural, Agrario y Alimentario (IMIDRA), Argelander-Institut für Astronomie (AlfA), Rheinische Friedrich-Wilhelms-Universität Bonn, Observatoire de Paris - Site de Paris (OP), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, European Project: 227610,EC:FP7:ERC,ERC-2008-AdG,LOFAR-AUGER(2009), European Project: 640130,H2020,ERC-2014-STG,LOFAR(2015), Radboud university [Nijmegen], Institute for Nuclear Physics (IKP), Karlsruhe Institute of Technology, nstitute for Nuclear Physics (IKP), Karlsruhe Institute of Technology, Université Paris 8 Vincennes-Saint-Denis (UP8)-Centre National de la Recherche Scientifique (CNRS)-Institut Galilée-Université Paris 13 (UP13), Universiteit Leiden [Leiden], Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), University of Oxford [Oxford], École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Research unit Astroparticle Physics, Astronomy, and Kapteyn Astronomical Institute
Subjects: TELESCOPE, High-energy astronomy, Astronomy, Astrophysics::High Energy Astrophysical Phenomena, Cosmic ray, Astrophysics, Electron, Astrophysics::Cosmology and Extragalactic Astrophysics, Radiation, EXTENSIVE AIR-SHOWERS, 01 natural sciences, 0103 physical sciences, 010303 astronomy & astrophysics, Astroparticle physics, Physics, Multidisciplinary, COSMIC cancer database, 010308 nuclear & particles physics, Astrophysics::Instrumentation and Methods for Astrophysics, LOFAR, ENERGY-SPECTRUM, SIMULATIONS, PULSES, High-energy astrophysics, Air shower, 13. Climate action, [SDU]Sciences of the Universe [physics], ARRAY, Neutrino, Particle astrophysics, EMISSION
Abstract: Cosmic rays are the highest-energy particles found in nature. Measurements of the mass composition of cosmic rays with energies of 1017–1018 electronvolts are essential to understanding whether they have galactic or extragalactic sources. It has also been proposed that the astrophysical neutrino signal1 comes from accelerators capable of producing cosmic rays of these energies2. Cosmic rays initiate air showers—cascades of secondary particles in the atmosphere—and their masses can be inferred from measurements of the atmospheric depth of the shower maximum3 (Xmax; the depth of the air shower when it contains the most particles) or of the composition of shower particles reaching the ground4. Current measurements5 have either high uncertainty, or a low duty cycle and a high energy threshold. Radio detection of cosmic rays6,7,8 is a rapidly developing technique9 for determining Xmax (refs 10, 11) with a duty cycle of, in principle, nearly 100 per cent. The radiation is generated by the separation of relativistic electrons and positrons in the geomagnetic field and a negative charge excess in the shower front6,12. Here we report radio measurements of Xmax with a mean uncertainty of 16 grams per square centimetre for air showers initiated by cosmic rays with energies of 1017–1017.5 electronvolts. This high resolution in Xmax enables us to determine the mass spectrum of the cosmic rays: we find a mixed composition, with a light-mass fraction (protons and helium nuclei) of about 80 per cent. Unless, contrary to current expectations, the extragalactic component of cosmic rays contributes substantially to the total flux below 1017.5 electronvolts, our measurements indicate the existence of an additional galactic component, to account for the light composition that we measured in the 1017–1017.5 electronvolt range.
Published: 2019

17. Needle-like structures discovered on positively charged lightning branches

Author: S. ter Veen, A. W. Gunst, M. A. Garrett, Laura Rossetto, A. J. van der Horst, J.-M. Grießmeier, R. Blaauw, Mark J. Bentum, R. J. van Weeren, Jörg P. Rachen, B. Ciardi, Pietro Zucca, Heino Falcke, R. Pekal, Aleksandar Shulevski, Anna Nelles, P. Maat, M. J. Norden, H. Paas, James M. Anderson, Stijn Buitink, Katie Mulrey, Richard Fallows, M. C. Toribio, J. Sluman, Luitje Koopmans, Olaf Scholten, Oleg Smirnov, Jörg R. Hörandel, Jochen Eislöffel, Roberto Pizzo, Hanna Rothkaehl, H. J. A. Röttgering, Harvey Butcher, P. Zarka, Olaf Wucknitz, Antonia Rowlinson, T. N. G. Trinh, Andrzej Krankowski, S. Duscha, Arthur Corstanje, Tim Huege, I. M. Avruch, Vishambhar Pandey, Ralph A. M. J. Wijers, M. Iacobelli, Pragati Mitra, Jason W. T. Hessels, Matthias Hoeft, A. van Ardenne, Tobias Winchen, Antonio Bonardi, Dominik J. Schwarz, W. N. Brouw, Brian Hare, Michel Tagger, W. Reich, J. W. Broderick, E. de Geus, Pim Schellart, Marcus Brüggen, M. P. van Haarlem, M. Pandey-Pommier, Joseph R. Dwyer, Marian Soida, High Energy Astrophys. & Astropart. Phys (API, FNWI), KVI Center for Advanced Radiation Technology, University of Groningen [Groningen], Radboud university [Nijmegen], Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), Netherlands Institute for Radio Astronomy (ASTRON), Astrophysical Institute, Vrije Universiteit Brussel, Vrije Universiteit [Brussels] (VUB), Karlsruher Institut für Technologie (KIT), Milieux aquatiques, écologie et pollutions (UR MALY), Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA), SRON Netherlands Institute for Space Research (SRON), University of Southampton, Kapteyn Astronomical Institute [Groningen], Jacobs University [Bremen], Research School of Astronomy and Astrophysics [Canberra] (RSAA), Australian National University (ANU), Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, Medstar Research Institute, Thüringer Landessternwarte Tautenburg (TLS), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Centre National d’Études Spatiales [Paris] (CNES), Unité Scientifique de la Station de Nançay (USN), Université d'Orléans (UO)-Observatoire des Sciences de l'Univers en région Centre (OSUC), PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), Leiden Observatory [Leiden], Universiteit Leiden [Leiden], Institute of Geodesy, Center for Information Technology CIT, Université de Groningen, Centre de Recherche Astrophysique de Lyon (CRAL), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-École normale supérieure - Lyon (ENS Lyon), Department of Applied Chemistry (DAC), Banaras Hindu University [Varanasi] (BHU), Max-Planck-Institut für Radioastronomie (MPIFR), Space Research Centre of Polish Academy of Sciences (CBK), Polska Akademia Nauk (PAN), Argelander-Institut für Astronomie (AlfA), Rheinische Friedrich-Wilhelms-Universität Bonn, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), European Project: 227610,EC:FP7:ERC,ERC-2008-AdG,LOFAR-AUGER(2009), European Project: 640130,H2020,ERC-2014-STG,LOFAR(2015), Center for Wireless Technology Eindhoven, Electromagnetics, EM for Radio Science Lab, Physics, Elementary Particle Physics, Astronomy and Astrophysics Research Group, Department of Bio-engineering Sciences, Faculty of Sciences and Bioengineering Sciences, Radboud University [Nijmegen], Vrije Universiteit Brussel (VUB), Global Aerospace, Adran Ffiseg, Prifysgol Cymru Aberystwyth, Universiteit Leiden, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Department of Physics the George Washington University, Space Radio-Diagnostic Research Center [Olsztyn], University of Warmia and Mazury [Olsztyn], Polska Akademia Nauk = Polish Academy of Sciences (PAN), Interactions Son Musique Mouvement, Sciences et Technologies de la Musique et du Son (STMS), Institut de Recherche et Coordination Acoustique/Musique (IRCAM)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche et Coordination Acoustique/Musique (IRCAM)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), Rhodes University, Grahamstown, Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Amsterdam [Amsterdam] (UvA), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Pierre et Marie Curie - Paris 6 (UPMC)-IRCAM-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-IRCAM-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Astronomy, and Research unit Astroparticle Physics
Subjects: [PHYS]Physics [physics], Physics, Multidisciplinary, 010504 meteorology & atmospheric sciences, Astronomy, 010502 geochemistry & geophysics, 01 natural sciences, Lightning, [SDU]Sciences of the Universe [physics], Natural phenomenon, ddc:530, Spatiotemporal resolution, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Initiation point, 0105 earth and related environmental sciences
Abstract: Nature / Physical science 568(7752), 360 - 363 (2019). doi:10.1038/s41586-019-1086-6, Lightning is a dangerous yet poorly understood natural phenomenon. Lightning forms a network of plasma channels propagating away from the initiation point with both positively and negatively charged ends—called positive and negative leaders. Negative leaders propagate in discrete steps, emitting copious radio pulses in the 30–300-megahertz frequency band that can be remotely sensed and imaged with high spatial and temporal resolution. Positive leaders propagate more continuously and thus emit very little high-frequency radiation. Radio emission from positive leaders has nevertheless been mapped, and exhibits a pattern that is different from that of negative leaders. Furthermore, it has been inferred that positive leaders can become transiently disconnected from negative leaders, which may lead to current pulses that both reconnect positive leaders to negative leaders and cause multiple cloud-to-ground lightning events. The disconnection process is thought to be due to negative differential resistance, but this does not explain why the disconnections form primarily on positive leaders, or why the current in cloud-to-ground lightning never goes to zero. Indeed, it is still not understood how positive leaders emit radio-frequency radiation or why they behave differently from negative leaders. Here we report three-dimensional radio interferometric observations of lightning over the Netherlands with unprecedented spatiotemporal resolution. We find small plasma structures—which we call ‘needles’—that are the dominant source of radio emission from the positive leaders. These structures appear to drain charge from the leader, and are probably the reason why positive leaders disconnect from negative ones, and why cloud-to-ground lightning connects to the ground multiple times., Published by Macmillan28177, London
Published: 2019

18. All‐sky interferometric riometry

Author: Anita Aikio, Richard Fallows, Farideh Honary, Juha Vierinen, Thomas Ulich, M. J. Norden, Derek McKay, and S. R. Marple
Subjects: Physics, COSMIC cancer database, Opacity, business.industry, Astrophysics::High Energy Astrophysical Phenomena, media_common.quotation_subject, Astrophysics::Instrumentation and Methods for Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Space weather, Condensed Matter Physics, Interferometry, Optics, Sky, Astrophysics::Solar and Stellar Astrophysics, General Earth and Planetary Sciences, Ionospheric absorption, Radio frequency, Electrical and Electronic Engineering, Ionosphere, business, Astrophysics::Galaxy Astrophysics, Remote sensing, media_common
Abstract: The first implementation of a Fourier-based interferometric riometry technique for measuring electron density induced ionospheric opacity at VHF radio frequencies is presented. Unlike multibeam riometers, which form discrete beams on the sky, the interferometric technique permits all-sky sampling of incoming cosmic radio noise emissions resulting in a spatially-continuous radiogram of the entire sky. The map of the received power at each time may then be compared to the equivalent map from a “quiet day”, allowing the morphology of ionospheric absorption of cosmic radio noise to be ascertained. In this work, the high-latitude Kilpisjarvi Atmospheric Imaging Receiver Array (KAIRA) was used to carry out the first interferometric riometry measurements in late 2013, producing all-sky absorption maps of space weather related ionization in the D region.
Published: 2015

19. Extreme intra-hour variability of the radio source J1402+5347 discovered with Apertif

Author: Kelley M. Hess, Henk Mulder, J. van Leeuwen, Tom Oosterloo, R. H. S. van den Brink, Stefan J. Wijnholds, M. J. Norden, J. Ziemke, Helga Denes, B. Adebahr, Yogesh Maan, B. Hut, L. C. Oostrum, R. Morganti, N. J. Vermaas, Elizabeth A. K. Adams, Vanessa A. Moss, A. M. Kutkin, Robert Schulz, J. M. van der Hulst, Emanuela Orru, D. M. Lucero, Harish Vedantham, W. J. G. de Blok, Dany Vohl, G. M. Loose, S. Damstra, A. R. Offringa, M. Ruiter, A. H. W. M. Coolen, Astronomy, Kapteyn Astronomical Institute, API Other Research (FNWI), and High Energy Astrophys. & Astropart. Phys (API, FNWI)
Subjects: Astrophysics::High Energy Astrophysical Phenomena, Milky Way, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, ISM: clouds, 01 natural sciences, Apparent magnitude, Angular diameter, 0103 physical sciences, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, Scintillation, 010308 nuclear & particles physics, scattering, Astronomy and Astrophysics, Light curve, Astrophysics - Astrophysics of Galaxies, Galaxy, Interstellar medium, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), Astrophysics - High Energy Astrophysical Phenomena, Radio wave
Abstract: The propagation of radio waves from distant compact radio sources through turbulent interstellar plasma in our Galaxy causes these sources to twinkle, a phenomenon called interstellar scintillation. Such scintillations are a unique probe of the micro-arcsecond structure of radio sources as well as of the sub-AU-scale structure of the Galactic interstellar medium. Weak scintillations (i.e. an intensity modulation of a few percent) on timescales of a few days or longer are commonly seen at centimetre wavelengths and are thought to result from the line-of-sight integrated turbulence in the interstellar plasma of the Milky Way. So far, only three sources were known that show more extreme variations, with modulations at the level of some dozen percent on timescales shorter than an hour. This requires propagation through nearby (d ~ 10^ 14K. }, Comment: Accepted for Astronomy and Astrophysics Letters
Published: 2020

20. KAIRA: The Kilpisjärvi Atmospheric Imaging Receiver Array—System Overview and First Results

Author: D. McKay-Bukowski, Markku Lehtinen, A. Schoenmakers, Jan Pieter de Reijer, Toivo Iinatti, Antti Kero, M. J. Norden, Nico Ebbendorf, Carl-Fredrik Enell, Mikko Orispää, Esa Turunen, Peter Gruppen, Henri Meulman, Olaf Wucknitz, Klaas Stuurwold, Markku Postila, Michiel A. Brentjens, T. Grit, Lassi Roininen, Juha Vierinen, Tero Raita, Thomas Ulich, Ilkka Virtanen, Richard Fallows, and Marchel Gerbers
Subjects: biology, Computer science, Incoherent scatter, Kaira, LOFAR, biology.organism_classification, law.invention, law, Observatory, Radar imaging, Very-long-baseline interferometry, General Earth and Planetary Sciences, Electrical and Electronic Engineering, Radar, Antenna (radio), Omnidirectional antenna, Radio astronomy, Remote sensing
Abstract: The Kilpisjarvi Atmospheric Imaging Receiver Array (KAIRA) is a dual array of omnidirectional VHF radio antennas located near Kilpisjarvi, Finland. It is operated by the Sodankyla Geophysical Observatory. It makes extensive use of the proven LOFAR antenna and digital signal-processing hardware, and can act as a stand-alone passive receiver, as a receiver for the European Incoherent Scatter (EISCAT) very high frequency (VHF) incoherent scatter radar in Tromso, or for use in conjunction with other Fenno-Scandinavian VHF experiments. In addition to being a powerful observing instrument in its own right, KAIRA will act as a pathfinder for technologies to be used in the planned EISCAT_3-D phased-array incoherent scatter radar system and participate in very long baseline interferometry experiments. This paper gives an overview of KAIRA, its principal hardware and software components, and its main science objectives. We demonstrate the applicability of the radio astronomy technology to our geoscience application. Furthermore, we present a selection of results from the commissioning phase of this new radio observatory.
Published: 2015

21. LOFAR discovery of a quiet emission mode in PSR B0823+26

Author: F. Breitling, Gottfried Mann, R. Pizzo, John D. Anderson, Cees Bassa, Sera Markoff, Rene P. Breton, Ashish Asgekar, Charlotte Sobey, E. Jütte, George Heald, Heino Falcke, P. Maat, M. J. Norden, M. A. Garrett, Jean-Mathias Grießmeier, Ph. Zarka, Rebecca McFadden, H. Paas, Ben Stappers, E. de Geus, Sarod Yatawatta, V. I. Kondratiev, D. D. Mulcahy, J. van Leeuwen, S. ter Veen, M. Pilia, M. Pandey-Pommier, Ralph A. M. J. Wijers, A. W. Gunst, J. Sluman, Olaf Wucknitz, H. J. A. Röttgering, Philip Best, Christian Vocks, D. McKay-Bukowski, Michel Tagger, D. Carbone, A. Alexov, Andrew Lyne, Antonia Rowlinson, A. Noutsos, Adam Stewart, Chiara Ferrari, T. E. Hassall, Evan Keane, Patrick Weltevrede, Jason W. T. Hessels, Satyendra Thoudam, S. Duscha, M. Serylak, A. van Duin, G. Pietka, Laura Birzan, Jochen Eislöffel, J. P. Hamaker, Wilfred Frieswijk, C. Toribio, Michael Kramer, D. A. Rafferty, A. G. Polatidis, Arthur Corstanje, A. Nelles, John D. Swinbank, Y. Tang, Anna M. M. Scaife, Martin Bell, N. J. Young, V. N. Pandey, Gerard H. Kuper, Cyril Tasse, J. W. Broderick, H. Munk, John McKean, Marcus Brüggen, Matthias Steinmetz, Annalisa Bonafede, A. Renting, Richard Fallows, R. Vermeulen, Mark J. Bentum, Matthias Hoeft, M. de Vos, Aris Karastergiou, Michael W. Wise, Gianni Bernardi, Jörg R. Hörandel, Rob Fender, Oleg Smirnov, Emanuela Orru, Dominik J. Schwarz, I. M. Avruch, Anna V. Bilous, R. J. van Weeren, Sobey, C., Young, N.J., Hessels, J.W.T., Weltevrede, P., Noutsos, A., Stappers, B.W., Kramer, M., Bassa, C., Lyne, A.G., Kondratiev V.I., null, Hassall, T.E., Keane, E.F., Bilous, A.V., Breton, R.P., Grießmeier, J.M., Karastergiou, A., Pilia, M., Serylak, M., Ter Veen, S., Van Leeuwen, J., Alexov, A., Anderson, J., Asgekar, A., Avruch, I.M., Bell, M.E., Bentum, M.J., Bernardi, G., Best, P., Bĭrzan, L., Bonafede, A., Breitling, F., Broderick, J., Brüggen, M., Corstanje, A., Carbone, D., De Geus, E., De Vos, M., Van Duin, A., Duscha, S., Eislöffel, J., Falcke, H., Fallows, R.A., Fender, R., Ferrari, C., Frieswijk, W., Garrett, M.A., Gunst, A.W., Hamaker, J.P., Heald, G., Hoeft, M., Hörandel, J., Jütte, E., Kuper, G., Maat, P., Mann, G., Markoff, S., McFadden, R., McKay-Bukowski, D., McKean, J.P., Mulcahy, D.D., Munk, H., Nelles, A., Norden, M.J., Orrù, E., Paas, H., Pandey-Pommier, M., Pandey, V.N., Pietka, G., Pizzo, R., Polatidis, A.G., Rafferty, D., Renting, A., Röttgering, H., Rowlinson, A., Scaife, A.M.M., Schwarz, D., Sluman, J., Smirnov, O., Steinmetz, M., Stewart, A., Swinbank, J., Tagger, M., Tang, Y., Tasse, C., Thoudam, S., Toribio, C., Vermeulen, R., Vocks, C., Van Weeren, R.J., Wijers, R.A.M.J., Wise, M.W., Wucknitz, O., Yatawatta, S., Zarka, P., Max-Planck-Institut für Radioastronomie (MPIFR), University of Minnesota [Twin Cities] (UMN), University of Minnesota System, University of Amsterdam [Amsterdam] (UvA), Jodrell Bank Centre for Astrophysics, University of Manchester [Manchester], Columbia Astrophysics Laboratory (CAL), Columbia University [New York], Cornell University [New York], Netherlands Institute for Radio Astronomy (ASTRON), Centre for Astrophysics and Supercomputing [Swinburne] (CAS), Swinburne University of Technology [Melbourne], Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), Radboud University [Nijmegen], Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Unité Scientifique de la Station de Nançay (USN), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Rhodes University, Grahamstown, Oxford Astrophysics, University of Oxford, Institute for Mathematics Applied to Geoscience, National Center for Atmospheric Research [Boulder] (NCAR), SRON Netherlands Institute for Space Research (SRON), CSIRO Astronomy and Space Science, Commonwealth Scientific and Industrial Research Organisation [Canberra] (CSIRO), Laboratoire de Physique Nucléaire et de Hautes Énergies (LPNHE), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), University of Edinburgh, Leiden Observatory [Leiden], Universiteit Leiden, Jacobs University [Bremen], Leibniz-Institut für Astrophysik Potsdam (AIP), University of Southampton, Medstar Research Institute, Thüringer Landessternwarte Tautenburg (TLS), Institute of Mathematical and Physical Sciences, Département de Géologie, Université de Montréal (UdeM), University Bochum, Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Oulu, Center for Information Technology CIT, Université de Groningen, Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), National Radio Astronomy Observatory [Charlottesville] (NRAO), National Radio Astronomy Observatory (NRAO), Department of Astronomy and Astrophysics [PennState], Pennsylvania State University (Penn State), Penn State System-Penn State System, School of Physics and Astronomy [Southampton], Interactions Son Musique Mouvement, Sciences et Technologies de la Musique et du Son (STMS), Institut de Recherche et Coordination Acoustique/Musique (IRCAM)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche et Coordination Acoustique/Musique (IRCAM)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), Leibniz-Institut DSMZ-Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH / Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures (DSMZ), Laboratory for Atmospheric and Space Physics [Boulder] (LASP), University of Colorado [Boulder], Université Paris-Sud - Paris 11 (UP11), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), SKA South Africa, Ska South Africa, Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University-Smithsonian Institution, Argelander-Institut für Astronomie (AlfA), Rheinische Friedrich-Wilhelms-Universität Bonn, We would like to thank R. Karuppusamy for his help with the Effelsberg observations. CF acknowledges financial support by the Agence Nationale de la Recherche through grant ANR-09-JCJC-0001-01., European Project: 337062,EC:FP7:ERC,ERC-2013-StG,DRAGNET(2014), ITA, GBR, FRA, DEU, NLD, Radboud university [Nijmegen], Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National d’Études Spatiales [Paris] (CNES), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO), University of Oxford [Oxford], Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Pierre et Marie Curie - Paris 6 (UPMC), Universiteit Leiden [Leiden], École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Harvard University [Cambridge]-Smithsonian Institution, Astronomy, and High Energy Astrophys. & Astropart. Phys (API, FNWI)
Subjects: stars, PSR B0823+26-radio telescopes, Astronomy, Astrophysics::High Energy Astrophysical Phenomena, Pulsar planet, FOS: Physical sciences, neutron- pulsars, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, neutron [stars], Pulsar, Millisecond pulsar, Pulsars: individual: PSR B0823+26, individual, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, Astroparticle physics, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy and Astrophysics, LOFAR, Astronomy and Astrophysic, Stars: neutron, Stars, Neutron star, Astrophysics - Solar and Stellar Astrophysics, magnetosphere-pulsars, [SDU]Sciences of the Universe [physics], Space and Planetary Science, QUIET, ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, Astrophysics - High Energy Astrophysical Phenomena, individual: PSR B0823+26 [pulsars]
Abstract: PSR B0823+26, a 0.53-s radio pulsar, displays a host of emission phenomena over timescales of seconds to (at least) hours, including nulling, subpulse drifting, and mode-changing. Studying pulsars like PSR B0823+26 provides further insight into the relationship between these various emission phenomena and what they might teach us about pulsar magnetospheres. Here we report on the LOFAR discovery that PSR B0823+26 has a weak and sporadically emitting 'quiet' (Q) emission mode that is over 100 times weaker (on average) and has a nulling fraction forty-times greater than that of the more regularly-emitting 'bright' (B) mode. Previously, the pulsar has been undetected in the Q-mode, and was assumed to be nulling continuously. PSR B0823+26 shows a further decrease in average flux just before the transition into the B-mode, and perhaps truly turns off completely at these times. Furthermore, simultaneous observations taken with the LOFAR, Westerbork, Lovell, and Effelsberg telescopes between 110 MHz and 2.7 GHz demonstrate that the transition between the Q-mode and B-mode occurs within one single rotation of the neutron star, and that it is concurrent across the range of frequencies observed., Comment: 15 pages, 8 figures, 2 tables, accepted for publication in MNRAS
Published: 2015

22. Corrigendum: A large light-mass component of cosmic rays at 10

Author: S, Buitink, A, Corstanje, H, Falcke, J R, Hörandel, T, Huege, A, Nelles, J P, Rachen, L, Rossetto, P, Schellart, O, Scholten, S, Ter Veen, S, Thoudam, T N G, Trinh, J, Anderson, A, Asgekar, I M, Avruch, M E, Bell, M J, Bentum, G, Bernardi, P, Best, A, Bonafede, F, Breitling, J W, Broderick, W N, Brouw, M, Brüggen, H R, Butcher, D, Carbone, B, Ciardi, J E, Conway, F, de Gasperin, E, de Geus, A, Deller, R-J, Dettmar, G, van Diepen, S, Duscha, J, Eislöffel, D, Engels, J E, Enriquez, R A, Fallows, R, Fender, C, Ferrari, W, Frieswijk, M A, Garrett, J M, Grießmeier, A W, Gunst, M P, van Haarlem, T E, Hassall, G, Heald, J W T, Hessels, M, Hoeft, A, Horneffer, M, Iacobelli, H, Intema, E, Juette, A, Karastergiou, V I, Kondratiev, M, Kramer, M, Kuniyoshi, G, Kuper, J, van Leeuwen, G M, Loose, P, Maat, G, Mann, S, Markoff, R, McFadden, D, McKay-Bukowski, J P, McKean, M, Mevius, D D, Mulcahy, H, Munk, M J, Norden, E, Orru, H, Paas, M, Pandey-Pommier, V N, Pandey, M, Pietka, R, Pizzo, A G, Polatidis, W, Reich, H J A, Röttgering, A M M, Scaife, D J, Schwarz, M, Serylak, J, Sluman, O, Smirnov, B W, Stappers, M, Steinmetz, A, Stewart, J, Swinbank, M, Tagger, Y, Tang, C, Tasse, M C, Toribio, R, Vermeulen, C, Vocks, C, Vogt, R J, van Weeren, R A M J, Wijers, S J, Wijnholds, M W, Wise, O, Wucknitz, S, Yatawatta, P, Zarka, and J A, Zensus
Published: 2016

23. LOFAR MSSS: detection of a low-frequency radio transient in 400 h of monitoring of the North Celestial Pole

Author: Rebecca McFadden, Martin Bell, Sera Markoff, G. Kokotanekov, R. J. van Weeren, D. McKay-Bukowski, James M. Anderson, Jason W. T. Hessels, Peter G. Jonker, Ralph A. M. J. Wijers, H. Munk, Casey J. Law, Frank Breitling, B. Scheers, Marcus Brüggen, M. C. Toribio, A. Horneffer, George Heald, M. A. Garrett, Aris Karastergiou, Luke Pratley, Rudy Wijnands, Y. Cendes, F. de Gasperin, A. Alexov, Michael W. Wise, Gianni Bernardi, Jörg R. Hörandel, B. Ciardi, M. Kuniyoshi, James Miller-Jones, J. van Leeuwen, T. Munoz-Darias, Aleksandar Shulevski, John McKean, J.-M. Grießmeier, John D. Swinbank, Jochen Eislöffel, P. Maat, Cyril Tasse, Wilfred Frieswijk, M. J. Norden, J. W. Broderick, A. G. Polatidis, Arthur Corstanje, T E Hassall, Heino Falcke, Harvey Butcher, E. de Geus, V. I. Kondratiev, E. Juette, Anna M. M. Scaife, M. Pandey-Pommier, Benjamin Stappers, H. Paas, A. W. Gunst, I. M. Avruch, Volker Heesen, D. Carbone, Mark J. Bentum, Antonia Rowlinson, Annalisa Bonafede, Rob Fender, J. Sluman, E. Rol, Matthias Steinmetz, Chiara Ferrari, Gijs Molenaar, S. Duscha, G. Kuper, D. D. Mulcahy, Sarod Yatawatta, Philip Best, M. Pietka, H. J. A. Röttgering, Satyendra Thoudam, A. O. Clarke, Adam Stewart, M. P. van Haarlem, Charlotte Sobey, M. Iacobelli, Olaf Wucknitz, Matthias Hoeft, Emanuela Orrú, M. Loose, Ph. Zarka, Adam Deller, Martin J. Hardcastle, Tim D. Staley, Ashish Asgekar, J. Moldon, Dominik J. Schwarz, A. J. van der Horst, Christian Vocks, Rene P. Breton, John Conway, Stephane Corbel, R. C. Vermeulen, Stefan J. Wijnholds, S. van Velzen, T. L. Grobler, Oleg Smirnov, Astronomy, Laboratory for Atmospheric and Space Physics [Boulder] (LASP), University of Colorado [Boulder], University of Southampton, Jodrell Bank Centre for Astrophysics, University of Manchester [Manchester], School of Physics and Astronomy [Southampton], Netherlands Institute for Radio Astronomy (ASTRON), Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Amsterdam [Amsterdam] (UvA), Oxford Astrophysics, University of Oxford [Oxford], Rhodes University, Grahamstown, CSIRO Astronomy and Space Science, Commonwealth Scientific and Industrial Research Organisation [Canberra] (CSIRO), Jacobs University [Bremen], Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), Unité Scientifique de la Station de Nançay (USN), Université d'Orléans (UO)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), Universität Hamburg (UHH), Thüringer Landessternwarte Tautenburg (TLS), Radboud university [Nijmegen], Département de Géologie, Université de Montréal [Montréal], Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), PSL Research University (PSL)-PSL Research University (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), University of Hertfordshire [Hatfield] (UH), Max-Planck-Institut für Radioastronomie (MPIFR), Leiden Observatory [Leiden], Universiteit Leiden [Leiden], Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), Curtin University [Perth], Planning and Transport Research Centre (PATREC), Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Victoria University of Wellington, Kapteyn Astronomical Institute [Groningen], University of Groningen [Groningen], SKA South Africa, Ska South Africa, Galaxies, Etoiles, Physique, Instrumentation (GEPI), PSL Research University (PSL)-PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), Department of Mathematics, The George Washington University, Washington State University (WSU), Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University [Cambridge]-Smithsonian Institution, Anton Pannekoek Institute for Astronomy, Observatoire de Paris - Site de Paris (OP), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Institute for Mathematics Applied to Geoscience, National Center for Atmospheric Research [Boulder] (NCAR), SRON Netherlands Institute for Space Research (SRON), Laboratoire de Physique Nucléaire et de Hautes Énergies (LPNHE), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), University of Edinburgh, Leibniz-Institut für Astrophysik Potsdam (AIP), Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, Onsala Space Observatory, Dept. of Radio and Space Science, Chalmers University of Technology, Chalmers University of Technology [Göteborg], Ruhr-Universität Bochum [Bochum], University of Oulu, The Netherlands Institute for Radio Astronomy (ASTRON), 7990-AA Dwingeloo, Netherlands, Departament d'Astronomia i Meteorologia [Barcelona], Institut de Ciènces del Cosmos (ICC), Universitat de Barcelona (UB)-Universitat de Barcelona (UB), Center for Information Technology CIT, Université de Groningen, Interactions Son Musique Mouvement, Sciences et Technologies de la Musique et du Son (STMS), Université Pierre et Marie Curie - Paris 6 (UPMC)-IRCAM-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-IRCAM-Centre National de la Recherche Scientifique (CNRS), Rhodes University, Leibniz-Institut DSMZ-Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH / Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures (DSMZ), Finca El Encin, Instituto Madrileño de Investigación y Desarrollo Rural, Agrario y Alimentario (IMIDRA), Argelander-Institut für Astronomie (AlfA), Rheinische Friedrich-Wilhelms-Universität Bonn, High Energy Astrophys. & Astropart. Phys (API, FNWI), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO), Université de Montréal (UdeM), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National d’Études Spatiales [Paris] (CNES), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Department of Mathematics [George Washington University] (GW), The George Washington University (GW), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Pierre et Marie Curie - Paris 6 (UPMC), Universitat de Barcelona (UB), Institut de Recherche et Coordination Acoustique/Musique (IRCAM)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche et Coordination Acoustique/Musique (IRCAM)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), University of Oxford, Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Radboud University [Nijmegen], Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Universiteit Leiden, École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Harvard University-Smithsonian Institution, Stewart, A.J., Fender, R.P., Broderick, J.W., Hassall, T.E., Muñoz-Darias, T., Rowlinson, A., Swinbank, J.D., Staley, T.D., Molenaar, G.J., Scheers, B., Grobler, T.L., Pietka, M., Heald, G., McKean, J.P., Bell, M.E., Bonafede, A., Breton, R.P., Carbone, D., Cendes, Y., Clarke, A.O., Corbel, S., De Gasperin, F., Eislöffel, J., Falcke, H., Ferrari, C., Grießmeier, J.-M., Hardcastle, M.J., Heesen, V., Hessels, J.W.T., Horneffer, A., Iacobelli, M., Jonker, P., Karastergiou, A., Kokotanekov, G., Kondratiev, V.I., Kuniyoshi, M., Law, C.J., van Leeuwen, J., Markoff, S., Miller-Jones, J.C.A., Mulcahy, D., Orru, E., Pandey-Pommier, M., Pratley, L., Rol, E., Röttgering, H.J.A., Scaife, A.M.M., Shulevski, A., Sobey, C.A., Stappers, B.W., Tasse, C., van der Horst, A.J., van Velzen, S., van Weeren, R.J., Wijers, R.A.M.J., Wijnands, R., Wise, M., Zarka, P., Alexov, A., Anderson, J., Asgekar, A., Avruch, I.M., Bentum, M.J., Bernardi, G., Best, P., Breitling, F., Brüggen, M., Butcher, H.R., Ciardi, B., Conway, J.E., Corstanje, A., de Geus, E., Deller, A., Duscha, S., Frieswijk, W., Garrett, M.A., Gunst, A.W., Van Haarlem, M.P., Hoeft, M., Hörandel, J., Juette, E., Kuper, G., Loose, M., Maat, P., McFadden, R., McKay-Bukowski, D., Moldon, J., Munk, H., Norden, M.J., Paas, H., Polatidis, A.G., Schwarz, D., Sluman, J., Smirnov, O., Steinmetz, M., Thoudam, S., Toribio, M.C., Vermeulen, R., Vocks, C., Wijnholds, S.J., Wucknitz, O., Yatawatta, S., ITA, GBR, FRA, DEU, and NLD
Subjects: Astronomy, media_common.quotation_subject, interferometers [instrumentation], radio continuum: general, FOS: Physical sciences, techniques: image processing, 02 engineering and technology, Astrophysics, Low frequency, 01 natural sciences, Instrumentation: interferometer, Celestial pole, 0103 physical sciences, IR-102656, 0202 electrical engineering, electronic engineering, information engineering, instrumentation: interferometers, Instrumentation and Methods for Astrophysics (astro-ph.IM), 010303 astronomy & astrophysics, media_common, EWI-27481, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, image processing [techniques], METIS-320906, 020206 networking & telecommunications, Astronomy and Astrophysics, LOFAR, Limiting, Astronomy and Astrophysic, instrumentation: interferometers – techniques: image processing – radio continuum: general, radio, continuum: general, Observation duration, Space and Planetary Science, Sky, [SDU]Sciences of the Universe [physics], ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, general [radio continuum], Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Instrumentation and Methods for Astrophysics
Abstract: We present the results of a four-month campaign searching for low-frequency radio transients near the North Celestial Pole with the Low-Frequency Array (LOFAR), as part of the Multifrequency Snapshot Sky Survey (MSSS). The data were recorded between 2011 December and 2012 April and comprised 2149 11-minute snapshots, each covering 175 deg^2. We have found one convincing candidate astrophysical transient, with a duration of a few minutes and a flux density at 60 MHz of 15-25 Jy. The transient does not repeat and has no obvious optical or high-energy counterpart, as a result of which its nature is unclear. The detection of this event implies a transient rate at 60 MHz of 3.9 (+14.7, -3.7) x 10^-4 day^-1 deg^-2, and a transient surface density of 1.5 x 10^-5 deg^-2, at a 7.9-Jy limiting flux density and ~10-minute time-scale. The campaign data were also searched for transients at a range of other time-scales, from 0.5 to 297 min, which allowed us to place a range of limits on transient rates at 60 MHz as a function of observation duration., 23 pages, 16 figures, 5 tables, accepted for publication in MNRAS
Published: 2016

24. Optimized trigger for ultra-high-energy cosmic-ray and neutrino observations with the low frequency radio array

Author: Y. Tang, Harvey Butcher, M. Drost, J. W. Romein, M. Pandey-Pommier, J. Morawietz, A. Renting, A. de Jong, J. Eisloeffel, M. A. Garrett, A. Doorduin, S. Yattawatta, Maaijke Mevius, Rebecca McFadden, K. Dijkstra, A. G. Polatidis, J. Sluman, W. A. van Cappellen, A. van Duin, Jean-Mathias Grießmeier, M. P. van Haarlem, Roberto Pizzo, H. Weggemans, Ben Stappers, Stijn Buitink, P. Maat, M. Loose, M. J. Norden, W. Reich, P. Bennema, C. Broekema, R. Nijboer, E. van der Wal, J. D. Mol, H.-J. Stiepel, H. A. Holties, L.A. Horneffer, H. Meulman, Rene C. Vermeulen, Olaf Wucknitz, J. van Leeuwen, R. H. van de Brink, P. Donker, P. Gruppen, Martin Bell, K. Stuurwold, Joel N. Bregman, G. Bernadi, E. Kooistra, H. Munk, T. Grit, G. Kuper, J. E. Noordam, J.-P. de Reijer, W. N. Brouw, Luitje Koopmans, M. Avruch, G. van Diepen, Heino Falcke, M. de Vos, Mark J. Bentum, B. Ciardi, C. Mallary, Matthias Hoeft, P. Riemers, Michel Tagger, K. Singh, S. ter Veen, A. W. Gunst, H. Paas, J. Roosjen, Ashish Asgekar, M. Ruiter, C. Vogt, Philip Best, M. Gerbers, Michel Arts, P. Lambropoulos, J. E. van Zwieten, Lambert J.M. Nieuwenhuis, E. Mulder, A. Huijgen, G. Schoonderbeek, D. Kant, S. Damstra, C. W. James, M. Brueggen, Albert-Jan Boonstra, A. P. Schoenmakers, A. H. W. M. Coolen, M. Steinmetz, R. J. Dettmar, Stefan J. Wijnholds, Y. Koopman, Olaf Scholten, Oleg Smirnov, R. Overeem, Michael W. Wise, Jörg R. Hörandel, J. M. Anderson, H. Roettgering, A. van Ardenne, Vishambhar Pandey, High Energy Astrophys. & Astropart. Phys (API, FNWI), Netherlands Institute for Radio Astronomy (ASTRON), University of Groningen [Groningen], Max-Planck-Institut für Radioastronomie (MPIFR), University of Southampton, University of Edinburgh, Kapteyn Astronomical Institute [Groningen], Radboud University [Nijmegen], Research School of Astronomy and Astrophysics [Canberra] (RSAA), Australian National University (ANU), Department of Reproduction and Development, Erasmus University Rotterdam, Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, London Institute for Mathematical Sciences, Astronomisches Institut der Ruhr-Universität Bochum, Ruhr-Universität Bochum [Bochum], Leiden Observatory [Leiden], Universiteit Leiden, Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Thüringer Landessternwarte Tautenburg (TLS), Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Amsterdam [Amsterdam] (UvA), DLR Institute of Aerospace Medicine, Deutsches Zentrum für Luft- und Raumfahrt [Köln] (DLR), Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Jodrell Bank Centre for Astrophysics (JBCA), University of Manchester [Manchester], Leibniz-Institut DSMZ-Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH / Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures (DSMZ), University of Reading (UOR), Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), Radboud university [Nijmegen], Universiteit Leiden [Leiden], École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), KVI - Center for Advanced Radiation Technology, Astronomy, and Kapteyn Astronomical Institute
Subjects: FLUX, Nuclear and High Energy Physics, Lunar radio detection, TELESCOPE, Astronomy, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Low frequency, UHE NEUTRINOS, 01 natural sciences, 7. Clean energy, law.invention, Radio telescope, Telescope, LIMITS, Frequency filter detection, law, SEARCH, 0103 physical sciences, Ultra-high-energy cosmic ray, 010306 general physics, Instrumentation and Methods for Astrophysics (astro-ph.IM), DETECTOR, 010303 astronomy & astrophysics, Instrumentation, Ultra-high energy neutrinos, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, SPECTRUM, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], Detector, Astrophysics::Instrumentation and Methods for Astrophysics, LOFAR, Ultra-high energy cosmic rays, [SDU]Sciences of the Universe [physics], ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, Neutrino, Nano-second pulse detection, Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, EMISSION, Energy (signal processing)
Abstract: When an ultra-high energy neutrino or cosmic ray strikes the Lunar surface a radio-frequency pulse is emitted. We plan to use the LOFAR radio telescope to detect these pulses. In this work we propose an efficient trigger implementation for LOFAR optimized for the observation of short radio pulses., Comment: Submitted to Nuclear Instruments and Methods in Physics Research Section A
Published: 2012

25. Imaging Jupiter's radiation belts down to 127 MHz with LOFAR

Author: Gianni Bernardi, Jörg R. Hörandel, A. G. Polatidis, Ashish Asgekar, A. Nelles, Angélica Sicard, H. Munk, R. J. van Weeren, Jason W. T. Hessels, D. McKay-Bukowski, I. de Pater, Matthias Hoeft, Oleg Smirnov, A. W. Gunst, Frank Breitling, Arthur Corstanje, Sebastien Hess, Quentin Nénon, Mark J. Bentum, J. van Leeuwen, R. C. Vermeulen, M. Loose, P. Zarka, H. J. A. Röttgering, P. Maat, M. J. Norden, M. Tagger, J. Moldón, F. de Gasperin, S. Bourdarie, Rene P. Breton, Annalisa Bonafede, John D. Swinbank, I. van Bemmel, Stephane Corbel, Martin Bell, V. I. Kondratiev, M. Pandey-Pommier, M. Iacobelli, James M. Anderson, Roberto Pizzo, Marcus Brüggen, Satyendra Thoudam, M. C. Toribio, Gerard H. Kuper, Antonia Rowlinson, Jochen Eislöffel, S. Duscha, Rebecca McFadden, M. A. Garrett, Daniel Santos-Costa, Julien N. Girard, Matthias Steinmetz, B. Ciardi, O. Wucknitz, J.-M. Grießmeier, M. Kuniyoshi, Ralph A. M. J. Wijers, Wilfred Frieswijk, Heino Falcke, C. Tasse, W. N. Brouw, S. Markov, Emanuela Orrú, H. Paas, Adam Deller, W. Reich, Dominik J. Schwarz, J. W. Broderick, E. Juette, G. Mann, Philip Best, C. Vocks, E. de Geus, Girard, J.N., Zarka, P., Tasse, C., Hess, S., De Pater, I., Santos-Costa, D., Nenon, Q., Sicard, A., Bourdarie, S., Anderson, J., Asgekar, A., Bell, M.E., Van Bemmel, I., Bentum, M.J., Bernardi, G., Best, P., Bonafede, A., Breitling, F., Breton, R.P., Broderick, J.W., Brouw, W.N., Brüggen, M., Ciardi, B., Corbel, S., Corstanje, A., De Gasperin, F., De Geus, E., Deller, A., Duscha, S., Eislöffel, J., Falcke, H., Frieswijk, W., Garrett, M.A., Grießmeier, J., Gunst, A.W., Hessels, J.W.T., Hoeft, M., Hörandel, J., Iacobelli, M., Juette, E., Kondratiev, V.I., Kuniyoshi, M., Kuper, G., Van Leeuwen, J., Loose, M., Maat, P., Mann, G., Markoff, S., McFadden, R., McKay-Bukowski, D., Moldon, J., Munk, H., Nelles, A., Norden, M.J., Orru, E., Paas, H., Pandey-Pommier, M., Pizzo, R., Polatidis, A.G., Reich, W., Röttgering, H., Rowlinson, A., Schwarz, D., Smirnov, O., Steinmetz, M., Swinbank, J., Tagger, M., Thoudam, S., Toribio, M.C., Vermeulen, R., Vocks, C., Van Weeren, R.J., Wijers, R.A.M.J., Wucknitz, O., Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Galaxies, Etoiles, Physique, Instrumentation (GEPI), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, ONERA - The French Aerospace Lab [Toulouse], ONERA, Netherlands Institute for Radio Astronomy (ASTRON), University of Southampton, Laboratoire de Physique Nucléaire et de Hautes Énergies (LPNHE (UMR_7585)), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Royal Observatory Edinburgh (ROE), University of Edinburgh, Jacobs University [Bremen], Leibniz-Institut für Astrophysik Potsdam (AIP), Jodrell Bank Centre for Astrophysics (JBCA), University of Manchester [Manchester], Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, Radboud University [Nijmegen], Hamburger Sternwarte/Hamburg Observatory, Universität Hamburg (UHH), Thüringer Landessternwarte Tautenburg (TLS), Leiden Observatory [Leiden], Universiteit Leiden, Unité Scientifique de la Station de Nançay (USN), Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Amsterdam [Amsterdam] (UvA), Department of Pure Mathematics and Mathematical Statistics (DPMMS), Faculty of mathematics Centre for Mathematical Sciences [Cambridge] (CMS), University of Cambridge [UK] (CAM)-University of Cambridge [UK] (CAM), Ruhr-Universität Bochum [Bochum], Max-Planck-Institut für Radioastronomie (MPIFR), University of Oulu, University of Groningen [Groningen], Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), CSIRO Astronomy and Space Science, Commonwealth Scientific and Industrial Research Organisation [Canberra] (CSIRO), Universität Bielefeld, Rhodes University, Grahamstown, Leibniz-Institut DSMZ-Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH / Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures (DSMZ), Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University-Smithsonian Institution, ANR-11-IDEX-0005,USPC,Université Sorbonne Paris Cité(2011), European Project: 228261,EC:FP7:ERC,ERC-2008-AdG,SPARSEASTRO(2009), ITA, GBR, FRA, DEU, NLD, Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), Radboud university [Nijmegen], Universiteit Leiden [Leiden], Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Harvard University [Cambridge]-Smithsonian Institution, Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), PSL Research University (PSL)-PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), Jodrell Bank Centre for Astrophysics, Université d'Orléans (UO)-Observatoire des Sciences de l'Univers en région Centre (OSUC), PSL Research University (PSL)-PSL Research University (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), PSL Research University (PSL)-PSL Research University (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), DPMMS/CMS, University of Cambridge [UK] (CAM), ANR-11-IDEX-0005-02/10-LABX-0023,UnivEarthS,Earth - Planets - Universe: observation, modeling, transfer(2011), Astronomy, High Energy Astrophys. & Astropart. Phys (API, FNWI), and Faculty of Science
Subjects: radio continuum: planetary systems, Brightness, 010504 meteorology & atmospheric sciences, radio continuum: planetary, EWI-27447, Astronomy, Astrophysics::High Energy Astrophysical Phenomena, Magnetosphere, FOS: Physical sciences, Astrophysics, Electron, METIS-321662, 7. Clean energy, 01 natural sciences, Jupiter, symbols.namesake, 0103 physical sciences, Emission spectrum, IR-103183, 010303 astronomy & astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), 0105 earth and related environmental sciences, Physics, Earth and Planetary Astrophysics (astro-ph.EP), [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], Radio continuum: planetary system, Planets and satellites: magnetic field, Astronomy and Astrophysics, LOFAR, Astronomy and Astrophysic, planets and satellites: magnetic fields, Spectral flux density, 13. Climate action, Space and Planetary Science, Van Allen radiation belt, Techniques: interferometric, symbols, ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, systems, Astrophysics::Earth and Planetary Astrophysics, Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - Earth and Planetary Astrophysics
Abstract: Context. Observing Jupiter's synchrotron emission from the Earth remains today the sole method to scrutinize the distribution and dynamical behavior of the ultra energetic electrons magnetically trapped around the planet (because in-situ particle data are limited in the inner magnetosphere). Aims. We perform the first resolved and low-frequency imaging of the synchrotron emission with LOFAR at 127 MHz. The radiation comes from low energy electrons (~1-30 MeV) which map a broad region of Jupiter's inner magnetosphere. Methods (see article for complete abstract) Results. The first resolved images of Jupiter's radiation belts at 127-172 MHz are obtained along with total integrated flux densities. They are compared with previous observations at higher frequencies and show a larger extent of the synchrotron emission source (>=4 $R_J$). The asymmetry and the dynamic of east-west emission peaks are measured and the presence of a hot spot at lambda_III=230 {\deg} $\pm$ 25 {\deg}. Spectral flux density measurements are on the low side of previous (unresolved) ones, suggesting a low-frequency turnover and/or time variations of the emission spectrum. Conclusions. LOFAR is a powerful and flexible planetary imager. The observations at 127 MHz depict an extended emission up to ~4-5 planetary radii. The similarities with high frequency results reinforce the conclusion that: i) the magnetic field morphology primarily shapes the brightness distribution of the emission and ii) the radiating electrons are likely radially and latitudinally distributed inside about 2 $R_J$. Nonetheless, the larger extent of the brightness combined with the overall lower flux density, yields new information on Jupiter's electron distribution, that may shed light on the origin and mode of transport of these particles., Comment: 10 pages, 12 figures, accepted for publication in A&A (27/11/2015) - abstract edited because of limited characters
Published: 2015

26. LOFAR sparse image reconstruction

Author: H. Garsden, J. N. Girard, J. L. Starck, S. Corbel, C. Tasse, A. Woiselle, J. P. McKean, A. S. van Amesfoort, J. Anderson, I. M. Avruch, R. Beck, M. J. Bentum, P. Best, F. Breitling, J. Broderick, M. Brüggen, H. R. Butcher, B. Ciardi, F. de Gasperin, E. de Geus, M. de Vos, S. Duscha, J. Eislöffel, D. Engels, H. Falcke, R. A. Fallows, R. Fender, C. Ferrari, W. Frieswijk, M. A. Garrett, J. Grießmeier, A. W. Gunst, T. E. Hassall, G. Heald, M. Hoeft, J. Hörandel, A. van der Horst, E. Juette, A. Karastergiou, V. I. Kondratiev, M. Kramer, M. Kuniyoshi, G. Kuper, G. Mann, S. Markoff, R. McFadden, D. McKay-Bukowski, D. D. Mulcahy, H. Munk, M. J. Norden, E. Orru, H. Paas, M. Pandey-Pommier, V. N. Pandey, G. Pietka, R. Pizzo, A. G. Polatidis, A. Renting, H. Röttgering, A. Rowlinson, D. Schwarz, J. Sluman, O. Smirnov, B. W. Stappers, M. Steinmetz, A. Stewart, J. Swinbank, M. Tagger, Y. Tang, S. Thoudam, C. Toribio, R. Vermeulen, C. Vocks, R. J. van Weeren, S. J. Wijnholds, M. W. Wise, O. Wucknitz, S. Yatawatta, P. Zarka, A. Zensus, Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), SAGEM Défense Sécurité [Massy], Netherlands Institute for Radio Astronomy (ASTRON), Delft University of Technology (TU Delft), SRON Netherlands Institute for Space Research (SRON), University of Edinburgh, Leibniz-Institut für Astrophysik Potsdam (AIP), Universität Hamburg (UHH), University of Southampton, Unité Scientifique de la Station de Nançay (USN), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), University of Oulu, Center for Information Technology CIT, Université de Groningen, Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), ANR-10-LABX-0023,UnivEarthS,Earth - Planets - Universe: observation, modeling, transfer(2010), ANR-11-IDEX-0005,USPC,Université Sorbonne Paris Cité(2011), ANR-09-JCJC-0001,OPALES(2009), European Project: 228261,EC:FP7:ERC,ERC-2008-AdG,SPARSEASTRO(2009), Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), High Energy Astrophys. & Astropart. Phys (API, FNWI), Rhodes University, SKA South Africa, Ska South Africa, Université d'Orléans (UO)-Observatoire des Sciences de l'Univers en région Centre (OSUC), PSL Research University (PSL)-PSL Research University (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), PSL Research University (PSL)-PSL Research University (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), ANR-10-LABX-0023,Labex UnivEarthS, ANR-11-IDEX-0005-02 ,USPC : Projet Université Sorbonne Paris Cité,Initiatives d’excellence - Laboratoire d’excellence INFLAMEX, and ANR-09-JCJC-0001,OPALES,nOn-thermal Processes in gALaxy cluStErs(2009)
Subjects: Sparse image, Phased array, Computer science, Aperture synthesis, Astronomy, EWI-26158, ComputingMethodologies_IMAGEPROCESSINGANDCOMPUTERVISION, FOS: Physical sciences, IR-96629, techniques: image processing, 02 engineering and technology, 01 natural sciences, methods: numerical, Radio telescope, symbols.namesake, 0103 physical sciences, 0202 electrical engineering, electronic engineering, information engineering, Angular resolution, GeneralLiterature_REFERENCE(e.g.,dictionaries,encyclopedias,glossaries), 010303 astronomy & astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), METIS-312678, Sparse matrix, image processing [techniques], Astrophysics::Instrumentation and Methods for Astrophysics, numerical [methods], 020206 networking & telecommunications, Astronomy and Astrophysics, LOFAR, Inverse problem, interferometric [techniques], Interferometry, techniques: interferometric – methods: numerical – techniques: image processing, techniques: image, Compressed sensing, Fourier transform, Space and Planetary Science, [SDU]Sciences of the Universe [physics], techniques: interferometric, symbols, processing, Deconvolution, Astrophysics - Instrumentation and Methods for Astrophysics, Algorithm
Abstract: Context. The LOw Frequency ARray (LOFAR) radio telescope is a giant digital phased array interferometer with multiple antennas distributed in Europe. It provides discrete sets of Fourier components of the sky brightness. Recovering the original brightness distribution with aperture synthesis forms an inverse problem that can be solved by various deconvolution and minimization methods Aims. Recent papers have established a clear link between the discrete nature of radio interferometry measurement and the "compressed sensing" (CS) theory, which supports sparse reconstruction methods to form an image from the measured visibilities. Empowered by proximal theory, CS offers a sound framework for efficient global minimization and sparse data representation using fast algorithms. Combined with instrumental direction-dependent effects (DDE) in the scope of a real instrument, we developed and validated a new method based on this framework Methods. We implemented a sparse reconstruction method in the standard LOFAR imaging tool and compared the photometric and resolution performance of this new imager with that of CLEAN-based methods (CLEAN and MS-CLEAN) with simulated and real LOFAR data Results. We show that i) sparse reconstruction performs as well as CLEAN in recovering the flux of point sources; ii) performs much better on extended objects (the root mean square error is reduced by a factor of up to 10); and iii) provides a solution with an effective angular resolution 2-3 times better than the CLEAN images. Conclusions. Sparse recovery gives a correct photometry on high dynamic and wide-field images and improved realistic structures of extended sources (of simulated and real LOFAR datasets). This sparse reconstruction method is compatible with modern interferometric imagers that handle DDE corrections (A- and W-projections) required for current and future instruments such as LOFAR and SKA, Published in A&A, 19 pages, 9 figures
Published: 2015

27. Calibrating the absolute amplitude scale for air showers measured at LOFAR

Author: A. Haungs, Stijn Buitink, A. Nelles, Olaf Scholten, Oleg Smirnov, Pim Schellart, George Heald, Jörg P. Rachen, Jörg R. Hörandel, Maria Krause, A. G. Polatidis, Emanuela Orrú, Wilfred Frieswijk, H. J. A. Röttgering, W. N. Brouw, Rebecca McFadden, Frank G. Schröder, J. Kohler, Katrin Link, R. Krause, P. Zarka, M. Iacobelli, J. Sluman, P. N. Best, P. Maat, M. J. Norden, Roberto Pizzo, Satyendra Thoudam, K. Weidenhaupt, M. P. van Haarlem, M. C. Toribio, Gerard H. Kuper, J. E. Enriquez, A. Horneffer, T. Karskens, Harvey Butcher, F. de Gasperin, J. D. Bregman, S. ter Veen, R. C. Vermeulen, Jochen Eislöffel, Heino Falcke, V. I. Kondratiev, M. Pandey-Pommier, H. Paas, E. Juette, M. Bruüggen, R. Hiller, W. Reich, James M. Anderson, Stefan J. Wijnholds, R. J. van Weeren, Arthur Corstanje, A. Karastergiou, B. Ciardi, Matthias Hoeft, D. McKay-Bukowski, Laura Rossetto, O. Wucknitz, T. N. G. Trinh, S. Duscha, C. Tasse, Martin Bell, M. Serylak, Mark J. Bentum, Tim Huege, J. van Leeuwen, M. Kuniyoshi, Vishambhar Pandey, D. Carbone, Ralph A. M. J. Wijers, Dominik J. Schwarz, Richard Fallows, M. A. Garrett, L. Bähren, Martin Erdmann, Annalisa Bonafede, Physics, Astronomy and Astrophysics Research Group, Elementary Particle Physics, Radboud university [Nijmegen], Institut de Génomique Fonctionnelle de Lyon (IGFL), École normale supérieure - Lyon (ENS Lyon)-Institut National de la Recherche Agronomique (INRA)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS), Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), Karlsruher Institut für Technologie - Campus Nord, Karlsruher Institut für Technologie - Campus Süd, Netherlands Institute for Radio Astronomy (ASTRON), Department of Astrophysics [Nijmegen], Radboud university [Nijmegen]-Radboud university [Nijmegen], University of Groningen [Groningen], Global Aerospace, Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Amsterdam [Amsterdam] (UvA), Jacobs University [Bremen], Kapteyn Astronomical Institute [Groningen], Research School of Astronomy and Astrophysics [Canberra] (RSAA), Australian National University (ANU), Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, Hamburger Sternwarte/Hamburg Observatory, Universität Hamburg (UHH), Thüringer Landessternwarte Tautenburg (TLS), Adran Ffiseg, Prifysgol Cymru Aberystwyth, Leiden Observatory [Leiden], Universiteit Leiden [Leiden], Joint Institute for VLBI in Europe (JIVE ERIC), DPMMS/CMS, University of Cambridge [UK] (CAM), Ruhr-Universität Bochum [Bochum], Oxford Astrophysics, University of Oxford [Oxford], Karlsruhe Institute of Technology (KIT), Max-Planck-Institut für Radioastronomie (MPIFR), University of Oulu, University of Groningen, Groningen, Netherlands, Centre de Recherche Astrophysique de Lyon (CRAL), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-École normale supérieure - Lyon (ENS Lyon), Department of Physics and Astronomy [South Africa], University of the Western Cape, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Aucun, Stichting WBBS, Argelander-Institut für Astronomie (AlfA), Rheinische Friedrich-Wilhelms-Universität Bonn, Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut National de la Recherche Agronomique (INRA)-École normale supérieure - Lyon (ENS Lyon), Department of Pure Mathematics and Mathematical Statistics (DPMMS), Faculty of mathematics Centre for Mathematical Sciences [Cambridge] (CMS), University of Cambridge [UK] (CAM)-University of Cambridge [UK] (CAM), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Radboud University [Nijmegen], École normale supérieure de Lyon (ENS de Lyon)-Institut National de la Recherche Agronomique (INRA)-Université Claude Bernard Lyon 1 (UCBL), Radboud University [Nijmegen]-Radboud University [Nijmegen], Universiteit Leiden, University of Oxford, École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), University of the Western Cape (UWC), High Energy Astrophys. & Astropart. Phys (API, FNWI), Research unit Astroparticle Physics, Astronomy, and Kapteyn Astronomical Institute
Subjects: Astronomy, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Cosmic ray, Astrophysics::Cosmology and Extragalactic Astrophysics, Optics, Calibration, ddc:610, Instrumentation and Methods for Astrophysics (astro-ph.IM), Instrumentation, Absolute scale, ComputingMilieux_MISCELLANEOUS, Mathematical Physics, High Energy Astrophysical Phenomena (astro-ph.HE), [PHYS]Physics [physics], Physics, business.industry, Astrophysics::Instrumentation and Methods for Astrophysics, LOFAR, Amplitude, Air shower, Experimental High Energy Physics, ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, Antennas, Radio frequency, Antenna (radio), Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], business
Abstract: Air showers induced by cosmic rays create nanosecond pulses detectable at radio frequencies. These pulses have been measured successfully in the past few years at the LOw Frequency ARray (LOFAR) and are used to study the properties of cosmic rays. For a complete understanding of this phenomenon and the underlying physical processes, an absolute calibration of the detecting antenna system is needed. We present three approaches that were used to check and improve the antenna model of LOFAR and to provide an absolute calibration of the whole system for air shower measurements. Two methods are based on calibrated reference sources and one on a calibration approach using the diffuse radio emission of the Galaxy, optimized for short data-sets. An accuracy of 19% in amplitude is reached. The absolute calibration is also compared to predictions from air shower simulations. These results are used to set an absolute energy scale for air shower measurements and can be used as a basis for an absolute scale for the measurement of astronomical transients with LOFAR., Comment: 34 pages, 10 figures
Published: 2015

28. Broadband meter-wavelength observations of ionospheric scintillation

Author: C.-F. Enell, Antti Kero, Michiel A. Brentjens, A. P. Schoenmakers, Nico Ebbendorf, M. Postila, Juha Vierinen, Markku Lehtinen, D. McKay-Bukowski, T. Grit, Mikko Orispää, Lassi Roininen, Tero Raita, T. Iinatti, M. Gerbers, William A. Coles, J-P. de Reijer, H. Meulman, Th. Ulich, Richard Fallows, P. Gruppen, Ilkka Virtanen, K. Stuurwold, M. J. Norden, and Esa Turunen
Subjects: Physics, Scintillation, 010504 meteorology & atmospheric sciences, FOS: Physical sciences, Astronomy, LOFAR, 01 natural sciences, F region, Atmospheric Sciences, Interstellar medium, Solar wind, Geophysics, Interplanetary scintillation, Astrophysics - Solar and Stellar Astrophysics, Pulsar, Space and Planetary Science, 0103 physical sciences, Physics::Space Physics, Ionosphere, Astrophysics - Instrumentation and Methods for Astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), 010303 astronomy & astrophysics, Astronomical and Space Sciences, Solar and Stellar Astrophysics (astro-ph.SR), 0105 earth and related environmental sciences
Abstract: Intensity scintillations of cosmic radio sources are used to study astrophysical plasmas like the ionosphere, the solar wind, and the interstellar medium. Normally these observations are relatively narrow band. With Low Frequency Array (LOFAR) technology at the Kilpisj\"arvi Atmospheric Imaging Receiver Array (KAIRA) station in northern Finland we have observed scintillations over a 3 octave bandwidth. ``Parabolic arcs'', which were discovered in interstellar scintillations of pulsars, can provide precise estimates of the distance and velocity of the scattering plasma. Here we report the first observations of such arcs in the ionosphere and the first broad-band observations of arcs anywhere, raising hopes that study of the phenomenon may similarly improve the analysis of ionospheric scintillations. These observations were made of the strong natural radio source Cygnus-A and covered the entire 30-250\,MHz band of KAIRA. Well-defined parabolic arcs were seen early in the observations, before transit, and disappeared after transit although scintillations continued to be obvious during the entire observation. We show that this can be attributed to the structure of Cygnus-A. Initial results from modeling these scintillation arcs are consistent with simultaneous ionospheric soundings taken with other instruments, and indicate that scattering is most likely to be associated more with the topside ionosphere than the F-region peak altitude. Further modeling and possible extension to interferometric observations, using international LOFAR stations, are discussed., Comment: 11 pages, 17 figures
Published: 2015

29. Measuring a Cherenkov ring in the radio emission from air showers at 110–190 MHz with LOFAR

Author: Aris Karastergiou, Gianni Bernardi, Jörg R. Hörandel, Adam Deller, A. Nelles, A. Horneffer, Jochen Eislöffel, Heino Falcke, Stefan J. Wijnholds, Gottfried Mann, J. E. Enriquez, Maaijke Mevius, B. Ciardi, Ben Stappers, Matthias Steinmetz, C. Tasse, Sarod Yatawatta, Olaf Scholten, Oleg Smirnov, Stijn Buitink, A. G. Polatidis, Arthur Corstanje, E. Juette, Adam Stewart, Christian Vocks, P. Zarka, M. Kuniyoshi, Rene C. Vermeulen, P. Maat, M. J. Norden, Harvey Butcher, Tim Hassall, Dominik J. Schwarz, V. I. Kondratiev, Joel N. Bregman, J. W. Broderick, Marcus Brüggen, M. Pandey-Pommier, George Heald, W. Reich, Michel Tagger, S. Duscha, J. Anderson, R. J. van Weeren, W. N. Brouw, M. van den Akker, G. Pietka, Wilfred Frieswijk, Philip Best, Pim Schellart, Y. Tang, Anna M. M. Scaife, K. D. de Vries, Ashish Asgekar, Martin Bell, S. ter Veen, A. W. Gunst, Marco Iacobelli, M. A. Garrett, G. Kuper, Frank Breitling, Richard Fallows, H. J. A. Röttgering, Mark J. Bentum, Olaf Wucknitz, Michael Kramer, H. Paas, Roberto Pizzo, Satyendra Thoudam, Physics, Elementary Particle Physics, Astronomy and Astrophysics Research Group, Radboud university [Nijmegen], SETI Institute, Netherlands Institute for Radio Astronomy (ASTRON), Max-Planck-Institut für Radioastronomie (MPIFR), Kernfysisch Versneller Instituut, Univ. of Groningen (KVI), University of Groningen [Groningen], Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), University of Southampton, Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University [Cambridge]-Smithsonian Institution, University of Edinburgh, Leibniz-Institut für Astrophysik Potsdam (AIP), Kapteyn Astronomical Institute [Groningen], Jacobs University [Bremen], Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, Thüringer Landessternwarte Tautenburg (TLS), Institute of Mathematical and Physical Sciences, Leiden Observatory [Leiden], Universiteit Leiden [Leiden], Jodrell Bank Centre for Astrophysics, University of Manchester [Manchester], Centre de Mathématiques Laurent Schwartz (CMLS), École polytechnique (X)-Centre National de la Recherche Scientifique (CNRS), Dipartimento di Matematica 'Guido Castelnuovo' [Roma I] (Sapienza University of Rome), Università degli Studi di Roma 'La Sapienza' [Rome], Ruhr-Universität Bochum [Bochum], Oxford Astrophysics, University of Oxford [Oxford], Vrije Universiteit Medical Centre (VUMC), Vrije Universiteit Amsterdam [Amsterdam] (VU), Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), School of Physics and Astronomy [Southampton], Interactions Son Musique Mouvement, Sciences et Technologies de la Musique et du Son (STMS), Université Pierre et Marie Curie - Paris 6 (UPMC)-IRCAM-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-IRCAM-Centre National de la Recherche Scientifique (CNRS), Rhodes University, Leibniz-Institut DSMZ-Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH / Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures (DSMZ), Laboratory for Atmospheric and Space Physics [Boulder] (LASP), University of Colorado [Boulder], Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Centre National d’Études Spatiales [Paris] (CNES), Sun Yat-Sen University (SYSU), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Argelander-Institut für Astronomie (AlfA), Rheinische Friedrich-Wilhelms-Universität Bonn, the Netherlands Research School for Astronomy (NOVA), the Samenwerkingsverband Noord-Nederland (SNN), the Foundation for Fundamental Research on Matter (FOM) and the Netherlands Organization for Scientific Research (NWO), VENI Grant 639-041-130., European Project: 227610,EC:FP7:ERC,ERC-2008-AdG,LOFAR-AUGER(2009), Radboud University [Nijmegen], Harvard University-Smithsonian Institution, Universiteit Leiden, Università degli Studi di Roma 'La Sapienza' = Sapienza University [Rome] (UNIROMA), University of Oxford, École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Rhodes University, Grahamstown, Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Sun Yat-Sen University [Guangzhou] (SYSU), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-École polytechnique (X), Università degli Studi di Roma 'La Sapienza' = Sapienza University [Rome], Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National d’Études Spatiales [Paris] (CNES), Research unit Astroparticle Physics, Astronomy, ITA, GBR, FRA, DEU, and NLD
Subjects: Astrophysics::High Energy Astrophysical Phenomena, Astronomy, FOS: Physical sciences, Cosmic ray, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Radiation, Radio telescope, Optics, cosmic rays, Extensive air showers, Radio emission, Instrumentation and Methods for Astrophysics (astro-ph.IM), Cherenkov radiation, High Energy Astrophysical Phenomena (astro-ph.HE), Astroparticle physics, Physics, astro-ph.HE, Range (particle radiation), business.industry, Astrophysics::Instrumentation and Methods for Astrophysics, Radio emissions, Astronomy and Astrophysics, LOFAR, Time-compression, [SDU]Sciences of the Universe [physics], Experimental High Energy Physics, ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, business, Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, Refractive index, astro-ph.IM
Abstract: Measuring radio emission from air showers offers a novel way to determine properties of the primary cosmic rays such as their mass and energy. Theory predicts that relativistic time compression effects lead to a ring of amplified emission which starts to dominate the emission pattern for frequencies above ~100 MHz. In this article we present the first detailed measurements of this structure. Ring structures in the radio emission of air showers are measured with the LOFAR radio telescope in the frequency range of 110 - 190 MHz. These data are well described by CoREAS simulations. They clearly confirm the importance of including the index of refraction of air as a function of height. Furthermore, the presence of the Cherenkov ring offers the possibility for a geometrical measurement of the depth of shower maximum, which in turn depends on the mass of the primary particle., 20 pages, 10 figures, accpeted for publication in Astroparticle Physics
Published: 2015

30. The LOFAR Multifrequency Snapshot Sky Survey (MSSS): I. Survey description and first results

Author: G. H. Heald, R. F. Pizzo, E. Orrú, R. P. Breton, D. Carbone, C. Ferrari, M. J. Hardcastle, W. Jurusik, G. Macario, D. Mulcahy, D. Rafferty, A. Asgekar, M. Brentjens, R. A. Fallows, W. Frieswijk, M. C. Toribio, B. Adebahr, M. Arts, M. R. Bell, A. Bonafede, J. Bray, J. Broderick, T. Cantwell, P. Carroll, Y. Cendes, A. O. Clarke, J. Croston, S. Daiboo, F. de Gasperin, J. Gregson, J. Harwood, T. Hassall, V. Heesen, A. Horneffer, A. J. van der Horst, M. Iacobelli, V. Jelić, D. Jones, D. Kant, G. Kokotanekov, P. Martin, J. P. McKean, L. K. Morabito, B. Nikiel-Wroczyński, A. Offringa, V. N. Pandey, M. Pandey-Pommier, M. Pietka, L. Pratley, C. Riseley, A. Rowlinson, J. Sabater, A. M. M. Scaife, L. H. A. Scheers, K. Sendlinger, A. Shulevski, M. Sipior, C. Sobey, A. J. Stewart, A. Stroe, J. Swinbank, C. Tasse, J. Trüstedt, E. Varenius, S. van Velzen, N. Vilchez, R. J. van Weeren, S. Wijnholds, W. L. Williams, A. G. de Bruyn, R. Nijboer, M. Wise, A. Alexov, J. Anderson, I. M. Avruch, R. Beck, M. E. Bell, I. van Bemmel, M. J. Bentum, G. Bernardi, P. Best, F. Breitling, W. N. Brouw, M. Brüggen, H. R. Butcher, B. Ciardi, J. E. Conway, E. de Geus, A. de Jong, M. de Vos, A. Deller, R.-J. Dettmar, S. Duscha, J. Eislöffel, D. Engels, H. Falcke, R. Fender, M. A. Garrett, J. Grießmeier, A. W. Gunst, J. P. Hamaker, J. W. T. Hessels, M. Hoeft, J. Hörandel, H. A. Holties, H. Intema, N. J. Jackson, E. Jütte, A. Karastergiou, W. F. A. Klijn, V. I. Kondratiev, L. V. E. Koopmans, M. Kuniyoshi, G. Kuper, C. Law, J. van Leeuwen, M. Loose, P. Maat, S. Markoff, R. McFadden, D. McKay-Bukowski, M. Mevius, J. C. A. Miller-Jones, R. Morganti, H. Munk, A. Nelles, J. E. Noordam, M. J. Norden, H. Paas, A. G. Polatidis, W. Reich, A. Renting, H. Röttgering, A. Schoenmakers, D. Schwarz, J. Sluman, O. Smirnov, B. W. Stappers, M. Steinmetz, M. Tagger, Y. Tang, S. ter Veen, S. Thoudam, R. Vermeulen, C. Vocks, C. Vogt, R. A. M. J. Wijers, O. Wucknitz, S. Yatawatta, P. Zarka, Heald, G.H., Pizzo, R.F., Orrú, E., Breton, R.P., Carbone, D., Ferrari, C., Hardcastle, M.J., Jurusik, W., Macario, G., Mulcahy, D., Rafferty, D., Asgekar, A., Brentjens, M., Fallows, R.A., Frieswijk, W., Toribio, M.C., Adebahr, B., Arts, M., Bell, M.R., Bonafede, A., Bray, J., Broderick, J., Cantwell, T., Carroll, P., Cendes, Y., Clarke, A.O., Croston, J., Daiboo, S., De Gasperin, F., Gregson, J., Harwood, J., Hassall, T., Heesen, V., Horneffer, A., Van Der Horst, A.J., Iacobelli, M., Jelić, V., Jones, D., Kant, D., Kokotanekov, G., Martin, P., McKean, J.P., Morabito, L.K., Nikiel-Wroczyński, B., Offringa, A., Pandey, V.N., Pandey-Pommier, M., Pietka, M., Pratley, L., Riseley, C., Rowlinson, A., Sabater, J., Scaife, A.M.M., Scheers, L.H.A., Sendlinger, K., Shulevski, A., Sipior, M., Sobey, C., Stewart, A.J., Stroe, A., Swinbank, J., Tasse, C., Trüstedt, J., Varenius, E., Van Velzen, S., Vilchez, N., Van Weeren, R.J., Wijnholds, S., Williams, W.L., De Bruyn, A.G., Nijboer, R., Wise, M., Alexov, A., Anderson, J., Avruch, I.M., Beck, R., Bell, M.E., Van Bemmel, I., Bentum, M.J., Bernardi, G., Best, P., Breitling, F., Brouw, W.N., Brüggen, M., Butcher, H.R., Ciardi, B., Conway, J.E., De Geus, E., De Jong, A., De Vos, M., Deller, A., Dettmar, R.-J., Duscha, S., Eislöffel, J., Engels, D., Falcke, H., Fender, R., Garrett, M.A., Grießmeier, J., Gunst, A.W., Hamaker, J.P., Hessels, J.W.T., Hoeft, M., Hörandel, J., Holties, H.A., Intema, H., Jackson, N.J., Jütte, E., Karastergiou, A., Klijn, W.F.A., Kondratiev, V.I., Koopmans, L.V.E., Kuniyoshi, M., Kuper, G., Law, C., Van Leeuwen, J., Loose, M., Maat, P., Markoff, S., McFadden, R., McKay-Bukowski, D., Mevius, M., Miller-Jones, J.C.A., Morganti, R., Munk, H., Nelles, A., Noordam, J.E., Norden, M.J., Paas, H., Polatidis, A.G., Reich, W., Renting, A., Röttgering, H., Schoenmakers, A., Schwarz, D., Sluman, J., Smirnov, O., Stappers, B.W., Steinmetz, M., Tagger, M., Tang, Y., Ter Veen, S., Thoudam, S., Vermeulen, R., Vocks, C., Vogt, C., Wijers, R.A.M.J., Wucknitz, O., Yatawatta, S., Zarka, P., High Energy Astrophys. & Astropart. Phys (API, FNWI), Netherlands Institute for Radio Astronomy (ASTRON), Jodrell Bank Centre for Astrophysics (JBCA), University of Manchester [Manchester], University of Hertfordshire [Hatfield] (UH), Uniwersytet Jagielloński w Krakowie = Jagiellonian University (UJ), Joseph Louis LAGRANGE (LAGRANGE), Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), University of Southampton, Jacobs University [Bremen], Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Amsterdam [Amsterdam] (UvA), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Hamburger Sternwarte/Hamburg Observatory, Universität Hamburg (UHH), School of Physics and Astronomy [Southampton], Leiden Observatory, Leiden University (Leiden Observatory), Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), CSIRO Astronomy and Space Science, Commonwealth Scientific and Industrial Research Organisation [Canberra] (CSIRO), Max-Planck-Institut für Radioastronomie (MPIFR), Laboratory for Atmospheric and Space Physics [Boulder] (LASP), University of Colorado [Boulder], Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Institut de recherche en astrophysique et planétologie (IRAP), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University-Smithsonian Institution, Leiden Observatory [Leiden], Universiteit Leiden, SRON Netherlands Institute for Space Research (SRON), Leibniz-Institut für Astrophysik Potsdam (AIP), Research School of Astronomy and Astrophysics [Canberra] (RSAA), Australian National University (ANU), Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, Los Alamos National Laboratory (LANL), Astronomisches Institut der Ruhr-Universität Bochum, Ruhr-Universität Bochum [Bochum], Thüringer Landessternwarte Tautenburg (TLS), Radboud University [Nijmegen], Unité Scientifique de la Station de Nançay (USN), Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Leibniz-Institut DSMZ-Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH / Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures (DSMZ), Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), ANR-09-JCJC-0001,OPALES(2009), European Project: 247295,EC:FP7:ERC,ERC-2009-AdG,AARTFAAC(2010), European Project: 267697,EC:FP7:ERC,ERC-2010-AdG_20100224,4PI-SKY(2011), ITA, GBR, FRA, DEU, NLD, Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Centre d'études européennes et de politique comparée (CEE), Sciences Po (Sciences Po)-Centre National de la Recherche Scientifique (CNRS), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Harvard University [Cambridge]-Smithsonian Institution, Universiteit Leiden [Leiden], Laboratoire de Physique Nucléaire et de Hautes Énergies (LPNHE (UMR_7585)), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Radboud university [Nijmegen], Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), Astronomy, Kapteyn Astronomical Institute, Jodrell Bank Centre for Astrophysics, Jagiellonian University [Krakow] (UJ), Université Nice Sophia Antipolis (... - 2019) (UNS), Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), Smithsonian Institution-Harvard University [Cambridge], Université d'Orléans (UO)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), PSL Research University (PSL)-PSL Research University (PSL)-Centre National d’Études Spatiales [Paris] (CNES), ANR-09-JCJC-0001,OPALES,nOn-thermal Processes in gALaxy cluStErs(2009), and Database Architectures
Subjects: 010504 meteorology & atmospheric sciences, Computer science, Astronomy, media_common.quotation_subject, FOS: Physical sciences, METIS-315082, 01 natural sciences, Radio spectrum, Radio continuum: general, surveys, 0103 physical sciences, radio continuum: general, Survey, GeneralLiterature_REFERENCE(e.g.,dictionaries,encyclopedias,glossaries), 010303 astronomy & astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), 0105 earth and related environmental sciences, Remote sensing, media_common, Giant Metrewave Radio Telescope, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], Astronomy and Astrophysics, LOFAR, Astronomy and Astrophysic, Square kilometre array, IR-98663, Sky, [SDU]Sciences of the Universe [physics], Space and Planetary Science, Experimental High Energy Physics, EWI-26540, Snapshot (computer storage), general [radio continuum], Astrophysics - Instrumentation and Methods for Astrophysics
Abstract: We present the Multifrequency Snapshot Sky Survey (MSSS), the first northern-sky LOFAR imaging survey. In this introductory paper, we first describe in detail the motivation and design of the survey. Compared to previous radio surveys, MSSS is exceptional due to its intrinsic multifrequency nature providing information about the spectral properties of the detected sources over more than two octaves (from 30 to 160 MHz). The broadband frequency coverage, together with the fast survey speed generated by LOFAR's multibeaming capabilities, make MSSS the first survey of the sort anticipated to be carried out with the forthcoming Square Kilometre Array (SKA). Two of the sixteen frequency bands included in the survey were chosen to exactly overlap the frequency coverage of large-area Very Large Array (VLA) and Giant Metrewave Radio Telescope (GMRT) surveys at 74 MHz and 151 MHz respectively. The survey performance is illustrated within the "MSSS Verification Field" (MVF), a region of 100 square degrees centered at J2000 (RA,Dec)=(15h,69deg). The MSSS results from the MVF are compared with previous radio survey catalogs. We assess the flux and astrometric uncertainties in the catalog, as well as the completeness and reliability considering our source finding strategy. We determine the 90% completeness levels within the MVF to be 100 mJy at 135 MHz with 108" resolution, and 550 mJy at 50 MHz with 166" resolution. Images and catalogs for the full survey, expected to contain 150,000-200,000 sources, will be released to a public web server. We outline the plans for the ongoing production of the final survey products, and the ultimate public release of images and source catalogs., Comment: 23 pages, 19 figures. Accepted for publication in Astronomy & Astrophysics. MSSS Verification Field images and catalog data may be downloaded from http://vo.astron.nl
Published: 2015

31. Lunar occultation of the diffuse radio sky: LOFAR measurements between 35 and 80 MHz

Author: Vibor Jelić, Martin Bell, Gottfried Mann, Michael W. Wise, Gianni Bernardi, Wilfred Frieswijk, Jörg R. Hörandel, Garrelt Mellema, J. W. Broderick, J. Anderson, E. de Geus, George Heald, Y. Tang, K. M. B. Asad, M. J. Norden, Heino Falcke, Michiel A. Brentjens, Luitje Koopmans, V. I. Kondratiev, Arthur Corstanje, de Antonius Bruyn, A. Renting, Michel Tagger, Ben Stappers, Elizabeth Fernandez, F. de Gasperin, S. Kazemi, Emanuela Orrú, O. Martinez-Rubi, Rob Fender, A. Nelles, Oleg Smirnov, Stefan J. Wijnholds, P. Lambropoulos, A. R. Offringa, Annalisa Bonafede, Emma Chapman, Hannes Jensen, E. Juette, D. Engels, Sera Markoff, C. Toribio, Abhik Ghosh, F. B. Abdalla, Rebecca McFadden, Roberto Pizzo, Marco Iacobelli, Sarod Yatawatta, S. Daiboo, Satyendra Thoudam, W. Reich, D. McKay-Bukowski, Dominik J. Schwarz, D. D. Mulcahy, A. H. Patil, Frank Breitling, Jochen Eislöffel, B. Ciardi, Maaijke Mevius, Mark J. Bentum, C. Tasse, V. Veligatla, A. G. Polatidis, Matthias Steinmetz, S. Bus, Vishambhar Pandey, M. Kuniyoshi, Philippe Zarka, S. ter Veen, Adam Deller, Chiara Ferrari, A. W. Gunst, Ashish Asgekar, Matthias Hoeft, Philip Best, A. Shulevski, John D. Swinbank, H. Munk, Marcus Brüggen, Geraint Harker, Jean-Mathias Grießmeier, Tim Hassall, Christian Vocks, Saleem Zaroubi, Rajat M. Thomas, John McKean, Harvey Butcher, M. Pandey-Pommier, S. Duscha, Harish Vedantham, Richard Fallows, M. A. Garrett, H. J. A. Röttgering, Olaf Wucknitz, G. Kuper, Kapteyn Astronomical Institute [Groningen], University of Groningen [Groningen], UMR Peuplement Végétaux et Bioagresseurs en Milieu Tropical (UMR PVBMT - INRA), Institut National de la Recherche Agronomique (INRA), Netherlands Institute for Radio Astronomy (ASTRON), University College of London [London] (UCL), Laboratoire de Mécanique des Contacts et des Structures [Villeurbanne] (LaMCoS), Institut National des Sciences Appliquées de Lyon (INSA Lyon), Université de Lyon-Institut National des Sciences Appliquées (INSA)-Université de Lyon-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS), Mécanique multiphysique pour les matériaux et les procédés (MULTIMAP), Université de Lyon-Institut National des Sciences Appliquées (INSA)-Université de Lyon-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées de Lyon (INSA Lyon), Laboratoire de Physique Nucléaire et de Hautes Énergies (LPNHE), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Howard Hugues Medical Institute, Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, Departamento de Geologıa, Universidad de Santiago de Chile [Santiago] (USACH), Advanced Computing and Microelectronics Unit [Kolkata] (ACMU), Indian Statistical Institute [Kolkata], Department of Physics and Astronomy [UCL London], Stockholm University, Department of process and energy, Delft University of Technology (TU Delft), Department of Physics, University of Crete [Heraklion] (UOC), Institute of Electronic Structure and Laser, Foundation for Research and Technology - Hellas (FORTH), Stockholm Observatory Department of Astronomy, Department of Physics and Astronomy [Ghent], Ghent University [Belgium] (UGENT), Spatial Ecology and Epidemiology Group, University of Oxford [Oxford], Plant Ind, Hort Unit, Commonwealth Scientific and Industrial Research Organisation [Canberra] (CSIRO), Institute for Mathematics Applied to Geoscience, National Center for Atmospheric Research [Boulder] (NCAR), CSIRO Astronomy and Space Science, University of Edinburgh, Jacobs University [Bremen], Leibniz-Institut für Astrophysik Potsdam (AIP), University of Southampton, Radboud university [Nijmegen], Hamburger Sternwarte/Hamburg Observatory, Universität Hamburg (UHH), Metacohorts Consortium, Thüringer Landessternwarte Tautenburg (TLS), Département de Géologie, Université de Montréal [Montréal], Leiden Observatory [Leiden], Universiteit Leiden [Leiden], Unité Scientifique de la Station de Nançay (USN), Université d'Orléans (UO)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), PSL Research University (PSL)-PSL Research University (PSL)-Centre National d’Études Spatiales [Paris] (CNES), Ruhr-Universität Bochum [Bochum], Max-Planck-Institut für Radioastronomie (MPIFR), Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Amsterdam [Amsterdam] (UvA), University of Oulu, Jodrell Bank Centre for Astrophysics, University of Manchester [Manchester], Centre de Recherche Astrophysique de Lyon (CRAL), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-École normale supérieure - Lyon (ENS Lyon), Interactions Son Musique Mouvement, Sciences et Technologies de la Musique et du Son (STMS), Université Pierre et Marie Curie - Paris 6 (UPMC)-IRCAM-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-IRCAM-Centre National de la Recherche Scientifique (CNRS), Rhodes University, Leibniz-Institut DSMZ-Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH / Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures (DSMZ), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Department of Astrophysics [Nijmegen], Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), Radboud university [Nijmegen]-Radboud university [Nijmegen], Argelander-Institut für Astronomie (AlfA), Rheinische Friedrich-Wilhelms-Universität Bonn, Observatoire de Paris - Site de Paris (OP), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS), European Project: 258942,EC:FP7:ERC,ERC-2010-StG_20091028,FIRSTLIGHT(2010), Howard Hughes Medical Institute (HHMI), Universiteit Gent = Ghent University (UGENT), University of Oxford, Radboud University [Nijmegen], Université de Montréal (UdeM), Universiteit Leiden, Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche et Coordination Acoustique/Musique (IRCAM)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche et Coordination Acoustique/Musique (IRCAM)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), Rhodes University, Grahamstown, Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Radboud University [Nijmegen]-Radboud University [Nijmegen], Agence Nationale de la Recherche (ANR-09-JCJC-0001-01), Peuplements végétaux et bioagresseurs en milieu tropical (UMR PVBMT), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut de Recherche pour le Développement (IRD)-Institut National de la Recherche Agronomique (INRA)-Université de La Réunion (UR), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Pierre et Marie Curie - Paris 6 (UPMC), Universiteit Gent = Ghent University [Belgium] (UGENT), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Vedantham, H.K., Koopmans, L.V.E., de Bruyn, A.G., Wijnholds, S.J., Brentjens, M., Abdalla, F.B., Asad, K.M.B., Bernardi, G., Bus, S., Chapman, E., Ciardi, B., Daiboo, S., Fernandez, E.R., Ghosh, A., Harker, G., Jelic, V., Jensen, H., Kazemi, S., Lambropoulos, P., Martinez-Rubi, O., Mellema, G., Mevius, M., Offringa, A.R., Pandey, V.N., Patil, A.H., Thomas, R.M., Veligatla, V., Yatawatta, S., Zaroubi, S., Anderson, J., Asgekar, A., Bell, M.E., Bentum, M.J., Best, P., Bonafede, A., Breitling, F., Broderick, J., Brüggen, M., Butcher, H.R., Corstanje, A., De Gasperin, F., De Geus, E., Deller, A., Duscha, S., Eislöffel, J., Engels, D., Falcke, H., Fallows, R.A., Fender, R., Ferrari, C., Frieswijk, W., Garrett, M.A., Grießmeier, J., Gunst, A.W., Hassall, T.E., Heald, G., Hoeft, M., Hörandel, J., Iacobelli, M., Juette, E., Kondratiev, V.I., Kuniyoshi, M., Kuper, G., Mann, G., Markoff, S., McFadden, R., McKay-Bukowski, D., McKean, J.P., Mulcahy, D.D., Munk, H., Nelles, A., Norden, M.J., Orru, E., Pandey-Pommier, M., Pizzo, R., Polatidis, A.G., Reich, W., Renting, A., Röttgering, H., Schwarz, D., Shulevski, A., Smirnov, O., Stappers, B.W., Steinmetz, M., Swinbank, J., Tagger, M., Tang, Y., Tasse, C., Ter Veen, S., Thoudam, S., Toribio, C., Vocks, C., Wise, M.W., Wucknitz, O., Zarka, P., Astronomy, Kapteyn Astronomical Institute, ITA, GBR, FRA, DEU, NLD, and High Energy Astrophys. & Astropart. Phys (API, FNWI)
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO), media_common.quotation_subject, Astrophysics::High Energy Astrophysical Phenomena, Astronomy, first stars, observational [methods], FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, methods: observational, techniques: interferometric, Moon, dark ages, reionization, methods: observational – techniques: interferometric – Moon – cosmology: dark ages, Occultation, IR-98655, Reionization, Instrumentation and Methods for Astrophysics (astro-ph.IM), media_common, EWI-26150, Astroparticle physics, Physics, Epoch (reference date), Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy and Astrophysics, LOFAR, Astronomy and Astrophysic, Universe, interferometric [techniques], Dark ages, reionization, first star, Sky, Space and Planetary Science, [SDU]Sciences of the Universe [physics], Physics::Space Physics, ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, Dark Ages, Astrophysics::Earth and Planetary Astrophysics, METIS-314921, Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract: We present radio observations of the Moon between $35$ and $80$ MHz to demonstrate a novel technique of interferometrically measuring large-scale diffuse emission extending far beyond the primary beam (global signal) for the first time. In particular, we show that (i) the Moon appears as a negative-flux source at frequencies $35z>12$) and the Epoch of Reionization ($12>z>5$)., Comment: 15 pages, 11 figures, 1 table
Published: 2015

32. Probing Atmospheric Electric Fields in Thunderstorms through Radio Emission from Cosmic-Ray-Induced Air Showers

Author: A. Alexov, M. Serylak, M. A. Garrett, E. Juette, B. Ciardi, C. Tasse, C. Koehn, M. Kuniyoshi, Dominik J. Schwarz, M. C. Toribio, A. Nelles, F. Breitling, Jean-Mathias Grießmeier, John McKean, John D. Swinbank, Jochen Eislöffel, W. Reich, J. Moldon, Maaijke Mevius, Marcus Brüggen, Casper Rutjes, R. J. van Weeren, Emanuela Orrú, J. W. Broderick, A. G. Polatidis, Rebecca McFadden, D. McKay-Bukowski, E. de Geus, Heino Falcke, M. J. Norden, V. I. Kondratiev, Harvey Butcher, M. Pandey-Pommier, Philip Best, Pim Schellart, Jason W. T. Hessels, Philippe Zarka, S. Duscha, Richard Fallows, Arthur Corstanje, Matthias Steinmetz, H. Paas, Ute Ebert, G. Kuper, Olaf Scholten, H. J. A. Röttgering, Oleg Smirnov, R. Vermeulen, Annalisa Bonafede, Mark J. Bentum, Michel Tagger, Michael W. Wise, Jörg P. Rachen, Gianni Bernardi, Jörg R. Hörandel, H. A. Holties, Olaf Wucknitz, T. N. G. Trinh, J. E. Enriquez, S. ter Veen, A. W. Gunst, M. de Vos, I. M. Avruch, Laura Rossetto, James M. Anderson, Gottfried Mann, Stijn Buitink, Roberto Pizzo, Wilfred Frieswijk, Christian Vocks, Satyendra Thoudam, Anna M. M. Scaife, Matthias Hoeft, George Heald, Department of Astrophysics [Nijmegen], Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), Radboud University [Nijmegen]-Radboud University [Nijmegen], KVI Center for Advanced Radiation Technology, University of Groningen [Groningen], Netherlands Institute for Radio Astronomy (ASTRON), Max-Planck-Institut für Radioastronomie (MPIFR), National Institute for Subatomic Physics [Amsterdam] (NIKHEF), Vrije Universiteit Brussel (VUB), Centrum Wiskunde & Informatica (CWI), Space Telescope Science Institute (STSci), GeoForschungsZentrum - Helmholtz-Zentrum Potsdam (GFZ), SRON Netherlands Institute for Space Research (SRON), Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University-Smithsonian Institution, Institute for Astronomy [Edinburgh] (IfA), University of Edinburgh, University of Hamburg, Leibniz-Institut für Astrophysik Potsdam (AIP), Oxford Astrophysics, University of Oxford, University of Southampton, Research School of Astronomy and Astrophysics [Canberra] (RSAA), Australian National University (ANU), Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, Thüringer Landessternwarte Tautenburg (TLS), Unité Scientifique de la Station de Nançay (USN), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Astronomisches Institut der Ruhr-Universität Bochum, Ruhr-Universität Bochum [Bochum], National Astronomical Observatory of Japan (NAOJ), University of Oulu, Center for Information Technology CIT, Université de Groningen, Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Leiden Observatory [Leiden], Universiteit Leiden, Universität Bielefeld = Bielefeld University, SKA South Africa, Ska South Africa, Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Amsterdam [Amsterdam] (UvA), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), NOVA, SNN and FOM as well as from NWO, VENI Grant No. 639-041-130, European Project: 227610,EC:FP7:ERC,ERC-2008-AdG,LOFAR-AUGER(2009), High Energy Astrophys. & Astropart. Phys (API, FNWI), Schellart, P., Trinh, T.N.G., Buitink, S., Corstanje, A., Enriquez, J.E., Falcke, H., Hörandel, J.R., Nelles, A., Rachen, J.P., Rossetto, L., Scholten, O., Ter Veen, S., Thoudam, S., Ebert, U., Koehn, C., Rutjes, C., Alexov, A., Anderson, J.M., Avruch, I.M., Bentum, M.J., Bernardi, G., Best, P., Bonafede, A., Breitling, F., Broderick, J.W., Brüggen, M., Butcher, H.R., Ciardi, B., De Geus, E., De Vos, M., Duscha, S., Eislöffel, J., Fallows, R.A., Frieswijk, W., Garrett, M.A., Grießmeier, J., Gunst, A.W., Heald, G., Hessels, J.W.T., Hoeft, M., Holties, H.A., Juette, E., Kondratiev, V.I., Kuniyoshi, M., Kuper, G., Mann, G., McFadden, R., McKay-Bukowski, D., McKean, J.P., Mevius, M., Moldon, J., Norden, M.J., Orru, E., Paas, H., Pandey-Pommier, M., Pizzo, R., Polatidis, A.G., Reich, W., Röttgering, H., Scaife, A.M.M., Schwarz, D.J., Serylak, M., Smirnov, O., Steinmetz, M., Swinbank, J., Tagger, M., Tasse, C., Toribio, M.C., Van Weeren, R.J., Vermeulen, R., Vocks, C., Wise, M.W., Wucknitz, O., Zarka, P., Kapteyn Astronomical Institute, Elementary Processes in Gas Discharges, Center for Wireless Technology Eindhoven, Physics, Astronomy and Astrophysics Research Group, Elementary Particle Physics, Multiscale Dynamics, Radboud university [Nijmegen]-Radboud university [Nijmegen], Harvard University [Cambridge]-Smithsonian Institution, University of Oxford [Oxford], Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National d’Études Spatiales [Paris] (CNES), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Universiteit Leiden [Leiden], Fakultät für Physik, Universität Bielefeld, Universität Bielefeld, ITA, GBR, FRA, DEU, and NLD
Subjects: Astronomy, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, General Physics and Astronomy, Cosmic ray, Astrophysics, Neutrino muon pion and other elementary particles, Physics and Astronomy (all), cosmic rays, IR-99169, Atmospheric electricity lightning, Electric field, Extensive air showers, Instrumentation and Methods for Astrophysics (astro-ph.IM), METIS-315601, Physics::Atmospheric and Oceanic Physics, High Energy Astrophysical Phenomena (astro-ph.HE), Earth and Planetary Astrophysics (astro-ph.EP), Astroparticle physics, Physics, [PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph], [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, EWI-26542, LOFAR, Polarization (waves), SIMULATIONS, COREAS, 13. Climate action, Experimental High Energy Physics, Thunderstorm, ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, ARRAY, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - Earth and Planetary Astrophysics
Abstract: We present measurements of radio emission from cosmic ray air showers that took place during thunderstorms. The intensity and polarization patterns of these air showers are radically different from those measured during fair-weather conditions. With the use of a simple two-layer model for the atmospheric electric field, these patterns can be well reproduced by state-of-the-art simulation codes. This in turn provides a novel way to study atmospheric electric fields., 6 pages, 3 figures, accepted for publication in Physical Review Letters
Published: 2015

33. The shape of the radio wavefront of extensive air showers as measured with LOFAR

Author: J. E. Enriquez, Wilfred Frieswijk, Y. Tang, Anna M. M. Scaife, Emanuela Orrú, Gottfried Mann, M. van den Akker, H. J. A. Röttgering, Stefan J. Wijnholds, W. Reich, Mark J. Bentum, Olaf Wucknitz, Sarod Yatawatta, Heino Falcke, Frank Breitling, Chiara Ferrari, D. Engels, Adam Stewart, Aris Karastergiou, Richard Fallows, Maria Krause, P. Maat, A. Horneffer, C. Toribio, Michel Tagger, M. A. Garrett, Jörg P. Rachen, Gianni Bernardi, Jörg R. Hörandel, M. J. Norden, Vishambhar Pandey, Matthias Hoeft, R. J. van Weeren, Jochen Eislöffel, V. I. Kondratiev, D. McKay-Bukowski, Marco Iacobelli, F. de Gasperin, A. Alexov, J.-M. Grießmeier, Maaijke Mevius, T. N. G. Trinh, G. Kuper, A. G. Polatidis, Arthur Corstanje, A. Nelles, E. Juette, I. M. Avruch, Roberto Pizzo, Olaf Scholten, Oleg Smirnov, J. Kohler, H. Paas, Satyendra Thoudam, M. de Vos, Dominik J. Schwarz, Rene C. Vermeulen, P. Zarka, Annalisa Bonafede, J. P. Hamaker, Martin Bell, J. Anderson, Matthias Steinmetz, S. ter Veen, Rebecca McFadden, A. W. Gunst, Stijn Buitink, Christian Vocks, J. W. Broderick, E. de Geus, John D. Swinbank, Harvey Butcher, M. Pandey-Pommier, S. Duscha, B. Ciardi, C. Tasse, M. Kuniyoshi, H. Munk, Marcus Brüggen, Philip Best, Pim Schellart, Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), Radboud University [Nijmegen], Netherlands Institute for Radio Astronomy (ASTRON), Max-Planck-Institut für Extraterrestrische Physik (MPE), Leibniz-Institut für Astrophysik Potsdam (AIP), SRON Netherlands Institute for Space Research (SRON), Delft University of Technology (TU Delft), University of Edinburgh, University of Southampton, Universität Hamburg (UHH), Thüringer Landessternwarte Tautenburg (TLS), Joseph Louis LAGRANGE (LAGRANGE), Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Unité Scientifique de la Station de Nançay (USN), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Universiteit Leiden, Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Leiden Observatory [Leiden], Department of Astrophysical Sciences [Princeton], Princeton University, Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Amsterdam [Amsterdam] (UvA), Netherlands Research School for Astronomy (NOVA), the Samenwerkingsverband Noord-Nederland (SNN) and the Foundation for Fundamental Research on Matter (FOM) as well as support from the Netherlands Organization for Scientific Research (NWO), VENI grant 639-041-130, European Project: 227610,EC:FP7:ERC,ERC-2008-AdG,LOFAR-AUGER(2009), ITA, GBR, FRA, DEU, NLD, Corstanje, A., Schellart, P., Nelles, A., Buitink, S., Enriquez, J.E., Falcke, H., Frieswijk, W., Hörandel, J.R., Krause, M., Rachen, J.P., Scholten, O., Ter Veen, S., Thoudam, S., Trinh, T.N.G., Van Den Akker, M., Alexov, A., Anderson, J., Avruch, I.M., Bell, M.E., Bentum, M.J., Bernardi, G., Best, P., Bonafede, A., Breitling, F., Broderick, J., Brüggen, M., Butcher, H.R., Ciardi, B., De Gasperin, F., De Geus, E., De Vos, M., Duscha, S., Eislöffel, J., Engels, D., Fallows, R.A., Ferrari, C., Garrett, M.A., Grießmeier, J., Gunst, A.W., Hamaker, J.P., Hoeft, M., Horneffer, A., Iacobelli, M., Juette, E., Karastergiou, A., Kohler, J., Kondratiev, V.I., Kuniyoshi, M., Kuper, G., Maat, P., Mann, G., McFadden, R., McKay-Bukowski, D., Mevius, M., Munk, H., Norden, M.J., Orru, E., Paas, H., Pandey-Pommier, M., Pandey, V.N., Pizzo, R., Polatidis, A.G., Reich, W., Röttgering, H., Scaife, A.M.M., Schwarz, D., Smirnov, O., Stewart, A., Steinmetz, M., Swinbank, J., Tagger, M., Tang, Y., Tasse, C., Toribio, C., Vermeulen, R., Vocks, C., Van Weeren, R.J., Wijnholds, S.J., Wucknitz, O., Yatawatta, S., Zarka, P., Radboud university [Nijmegen], Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), Universiteit Leiden [Leiden], École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Astronomy, Research unit Astroparticle Physics, and High Energy Astrophys. & Astropart. Phys (API, FNWI)
Subjects: Physics::Instrumentation and Detectors, Astronomy, Astrophysics::High Energy Astrophysical Phenomena, Extensive air shower, FOS: Physical sciences, Cosmic ray, Astrophysics, 01 natural sciences, Radio telescope, Optics, 0103 physical sciences, Extensive air showers, Ultra-high-energy cosmic ray, Radio emission, 010303 astronomy & astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), Cosmic rays, Wavefront, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), 010308 nuclear & particles physics, business.industry, [SDU.ASTR.HE]Sciences of the Universe [physics]/Astrophysics [astro-ph]/High Energy Astrophysical Phenomena [astro-ph.HE], Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy and Astrophysics, LOFAR, Air shower, Wavefront shape, ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, Hyperboloid, business, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Instrumentation and Methods for Astrophysics, Shape analysis (digital geometry)
Abstract: Extensive air showers, induced by high energy cosmic rays impinging on the Earth's atmosphere, produce radio emission that is measured with the LOFAR radio telescope. As the emission comes from a finite distance of a few kilometers, the incident wavefront is non-planar. A spherical, conical or hyperbolic shape of the wavefront has been proposed, but measurements of individual air showers have been inconclusive so far. For a selected high-quality sample of 161 measured extensive air showers, we have reconstructed the wavefront by measuring pulse arrival times to sub-nanosecond precision in 200 to 350 individual antennas. For each measured air shower, we have fitted a conical, spherical, and hyperboloid shape to the arrival times. The fit quality and a likelihood analysis show that a hyperboloid is the best parametrization. Using a non-planar wavefront shape gives an improved angular resolution, when reconstructing the shower arrival direction. Furthermore, a dependence of the wavefront shape on the shower geometry can be seen. This suggests that it will be possible to use a wavefront shape analysis to get an additional handle on the atmospheric depth of the shower maximum, which is sensitive to the mass of the primary particle., Accepted for publication in Astroparticle Physics
Published: 2014

34. Initial LOFAR observations of epoch of reionization windows. II. Diffuse polarized emission in the ELAIS-N1 field

Author: F. de Gasperin, A. Horneffer, Jochen Eislöffel, M. A. Garrett, Geraint Harker, Michael Kramer, A. Nelles, J. van Leeuwen, Maaijke Mevius, Wilfred Frieswijk, Y. Tang, Anna M. M. Scaife, S. ter Veen, J. P. Hamaker, V. Veligatla, Marijke Haverkorn, G. Mann, A. W. Gunst, Chiara Ferrari, Rob Fender, D. Engels, Philip Best, Harish Vedantham, A. R. Offringa, John Conway, M. Iacobelli, M. Serylak, E. Juette, Hannes Jensen, James M. Anderson, C. Vocks, Annalisa Bonafede, Heino Falcke, Vibor Jelić, R. J. Dettmar, John McKean, Matthias Hoeft, A. H. Patil, J. W. Broderick, Saleem Zaroubi, P. Maat, Tim Hassall, Harvey Butcher, Aris Karastergiou, H. J. A. Röttgering, Rajat M. Thomas, M. J. Norden, V. I. Kondratiev, Olaf Wucknitz, M. Pandey-Pommier, H. Paas, Gianni Bernardi, Jörg R. Hörandel, Mark J. Bentum, Antonia Rowlinson, Michel Tagger, Garrelt Mellema, H. Munk, C. Tasse, O. Martinez-Rubi, W. Reich, J. D. Bregman, S. Kazemi, Abhik Ghosh, George Heald, Oleg Smirnov, Elizabeth Fernandez, S. Duscha, Dominik J. Schwarz, A. G. Polatidis, I. M. Avruch, Michiel A. Brentjens, W. N. Brouw, Roberto Pizzo, P. Labropoulos, Marcus Brüggen, Ralph A. M. J. Wijers, G. Pietka, Gerard H. Kuper, K. M. B. Asad, Martin Bell, Satyendra Thoudam, Jean-Mathias Griessmeier, Richard Fallows, A. Alexov, Emma Chapman, Ron Beck, A. G. de Bruyn, Luitje Koopmans, Vishambhar Pandey, Adam Deller, C. Toribio, F. B. Abdalla, P. Zarka, Matthias Steinmetz, F. Breitling, B. Ciardi, Jason W. T. Hessels, S. Bus, M. Kuniyoshi, R. Vermeulen, Stefan J. Wijnholds, E. de Geus, Sarod Yatawatta, S. Daiboo, Adam Stewart, A. J. van der Horst, R. J. van Weeren, D. McKay-Bukowski, Netherlands Institute for Radio Astronomy (ASTRON), University College of London [London] (UCL), Laboratoire de Physique Nucléaire et de Hautes Énergies (LPNHE (UMR_7585)), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, University of Pennsylvania [Philadelphia], SRON Netherlands Institute for Space Research (SRON), Max-Planck-Institut für Radioastronomie (MPIFR), University of Southampton, University of Edinburgh, Jacobs University [Bremen], Leibniz-Institut für Astrophysik Potsdam (AIP), Thüringer Landessternwarte Tautenburg (TLS), Radboud university [Nijmegen], Joseph Louis LAGRANGE (LAGRANGE), Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Leiden Observatory [Leiden], Universiteit Leiden [Leiden], Unité Scientifique de la Station de Nançay (USN), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Jodrell Bank Centre for Astrophysics (JBCA), University of Manchester [Manchester], University of Amsterdam [Amsterdam] (UvA), Ruhr-Universität Bochum [Bochum], Vrije Universiteit Medical Centre (VUMC), Vrije Universiteit Amsterdam [Amsterdam] (VU), University of Oulu, Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), School of Physics and Astronomy [Southampton], Laboratory for Atmospheric and Space Physics [Boulder] (LASP), University of Colorado [Boulder], Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), Astronomical Institute Anton Pannekoek (AI PANNEKOEK), ANR-09-JCJC-0001,OPALES(2009), Jelić, V., De Bruyn, A.G., Mevius, M., Abdalla, F.B., Asad, K.M.B., Bernardi, G., Brentjens, M.A., Bus, S., Chapman, E., Ciardi, B., Daiboo, S., Fernandez, E.R., Ghosh, A., Harker, G., Jensen, H., Kazemi, S., Koopmans, L.V.E., Labropoulos, P., Martinez-Rubi, O., Mellema, G., Offringa, A.R., Pandey, V.N., Patil, A.H., Thomas, R.M., Vedantham, H.K., Veligatla, V., Yatawatta, S., Zaroubi, S., Alexov, A., Anderson, J., Avruch, I.M., Beck, R., Bell, M.E., Bentum, M.J., Best, P., Bonafede, A., Bregman, J., Breitling, F., Broderick, J., Brouw, W.N., Brüggen, M., Butcher, H.R., Conway, J.E., De Gasperin, F., De Geus, E., Deller, A., Dettmar, R.-J., Duscha, S., Eislöffel, J., Engels, D., Falcke, H., Fallows, R.A., Fender, R., Ferrari, C., Frieswijk, W., Garrett, M.A., Grießmeier, J., Gunst, A.W., Hamaker, J.P., Hassall, T.E., Haverkorn, M., Heald, G., Hessels, J.W.T., Hoeft, M., Hörandel, J., Horneffer, A., Van Der Horst, A., Iacobelli, M., Juette, E., Karastergiou, A., Kondratiev, V.I., Kramer, M., Kuniyoshi, M., Kuper, G., Van Leeuwen, J., Maat, P., Mann, G., McKay-Bukowski, D., McKean, J.P., Munk, H., Nelles, A., Norden, M.J., Paas, H., Pandey-Pommier, M., Pietka, G., Pizzo, R., Polatidis, A.G., Reich, W., Röttgering, H., Rowlinson, A., Scaife, A.M.M., Schwarz, D., Serylak, M., Smirnov, O., Steinmetz, M., Stewart, A., Tagger, M., Tang, Y., Tasse, C., Ter Veen, S., Thoudam, S., Toribio, C., Vermeulen, R., Vocks, C., Van Weeren, R.J., Wijers, R.A.M.J., Wijnholds, S.J., Wucknitz, O., Zarka, P., Astronomy, Kapteyn Astronomical Institute, University of Pennsylvania, Radboud University [Nijmegen], Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Universiteit Leiden, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), High Energy Astrophys. & Astropart. Phys (API, FNWI), Université Nice Sophia Antipolis (... - 2019) (UNS), Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Université d'Orléans (UO)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), PSL Research University (PSL)-PSL Research University (PSL)-Centre National d’Études Spatiales [Paris] (CNES), Jodrell Bank Centre for Astrophysics, Observatoire de Paris - Site de Paris (OP), PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), and ANR-09-JCJC-0001,OPALES,nOn-thermal Processes in gALaxy cluStErs(2009)
Subjects: Brightness, Astronomy, techniques, Astrophysics, Cosmology: observation, 01 natural sciences, EWI-25428, law.invention, law, polarimetric [techniques], dark ages, Faraday cage, 010303 astronomy & astrophysics, Physics, Line-of-sight, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], Astrophysics::Instrumentation and Methods for Astrophysics, Polarization (waves), observations [cosmology], interferometric [techniques], radio continuum: ISM, techniques: interferometric, Brightness temperature, ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, IR-93232, reionization, Astrophysics - Instrumentation and Methods for Astrophysics, techniques: polarimetric, cosmology: observations, diffuse radiation, first stars, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, ISM [radio continuum], Astrophysics::Cosmology and Extragalactic Astrophysics, Radio telescope, 0103 physical sciences, Instrumentation and Methods for Astrophysics (astro-ph.IM), Reionization, Astrophysics::Galaxy Astrophysics, 010308 nuclear & particles physics, Astronomy and Astrophysics, METIS-309730, LOFAR, Astronomy and Astrophysic, Astrophysics - Astrophysics of Galaxies, [SDU.ASTR.IM]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM], Dark ages, reionization, first star, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), polarimetric
Abstract: This study aims to characterise the polarized foreground emission in the ELAIS-N1 field and to address its possible implications for the extraction of the cosmological 21-cm signal from the Low-Frequency Array - Epoch of Reionization (LOFAR-EoR) data. We use the high band antennas of LOFAR to image this region and RM-synthesis to unravel structures of polarized emission at high Galactic latitudes. The brightness temperature of the detected Galactic emission is on average 4 K in polarized intensity and covers the range from -10 to +13rad m^-2 in Faraday depth. The total polarized intensity and polarization angle show a wide range of morphological features. We have also used the Westerbork Synthesis Radio Telescope (WSRT) at 350 MHz to image the same region. The LOFAR and WSRT images show a similar complex morphology, at comparable brightness levels, but their spatial correlation is very low. The fractional polarization at 150 MHz, expressed as a percentage of the total intensity, amounts to 1.5%. There is no indication of diffuse emission in total intensity in the interferometric data, in line with results at higher frequencies. The wide frequency range, good angular resolution and good sensitivity make LOFAR an exquisite instrument for studying Galactic polarized emission at a resolution of 1-2 rad m^-2 in Faraday depth. The different polarised patterns observed at 150 MHz and 350 MHz are consistent with different source distributions along the line of sight wring in a variety of Faraday thin regions of emission. The presence of polarised foregrounds is a serious complication for Epoch of Reionization experiments. To avoid the leakage of polarized emission into total intensity, which can depend on frequency, we need to calibrate the instrumental polarization across the field of view to a small fraction of 1%., 12 pages, 9 figures, accepted for publication in A&A
Published: 2014

35. Discovery of carbon radio recombination lines in absorption towards Cygnus A

Author: J. van Enst, D. Engels, J. B. R. Oonk, S. ter Veen, Tim Hassall, Leah K. Morabito, M. A. Garrett, Alexander G. G. M. Tielens, Ashish Asgekar, J. M. Anderson, Rainer Beck, D. D. Mulcahy, Neal Jackson, Frank Breitling, Vishambhar Pandey, Harvey Butcher, Rob Fender, James Miller-Jones, M. Pandey-Pommier, Sarod Yatawatta, Giulia Macario, Michel Tagger, J. Kohler, Anton Zensus, John Conway, H. J. A. Röttgering, Heino Falcke, H. Munk, Marcus Brüggen, A. Horneffer, Richard Fallows, Jochen Eislöffel, E. Juette, Olaf Wucknitz, P. Maat, M. J. Norden, A. Alexov, C. Vogt, Aris Karastergiou, Maaijke Mevius, G. Kuper, S. Duscha, V. I. Kondratiev, Michael W. Wise, Gianni Bernardi, Philip Best, Benjamin Stappers, Dominik J. Schwarz, Wilfred Frieswijk, Y. Tang, A. Shulevski, Anna M. M. Scaife, Chiara Ferrari, Glenn J. White, B. Ciardi, Marco Iacobelli, M. de Vos, Jean-Mathias Grießmeier, A. G. Polatidis, Arthur Corstanje, Matthias Hoeft, J. Sluman, John McKean, C. Tasse, John D. Swinbank, Francisco Salgado, J. W. Broderick, Roberto Pizzo, E. de Geus, Satyendra Thoudam, Ralph A. M. J. Wijers, Christian Vocks, Sera Markoff, C. Toribio, J. D. Mol, M. Kuniyoshi, Annalisa Bonafede, Jason W. T. Hessels, Michiel A. Brentjens, Mark J. Bentum, George Heald, Michael Kramer, J. van Leeuwen, Philippe Zarka, R. van Nieuwpoort, J. P. Hamaker, Charlotte Sobey, Emanuela Orrú, H. Paas, F. Batejat, W. Reich, Oleg Smirnov, F. de Gasperin, I. van Bemmel, Martin Bell, Gottfried Mann, Matthias Steinmetz, I. M. Avruch, R. J. van Weeren, Rene C. Vermeulen, Wouter Klijn, A. J. van der Horst, A. P. Schoenmakers, Netherlands Institute for Radio Astronomy (ASTRON), Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University-Smithsonian Institution, Leiden Observatory [Leiden], Universiteit Leiden, Department of Physics and Astronomy [Milton Keynes], The Open University [Milton Keynes] (OU), Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, SRON Netherlands Institute for Space Research (SRON), Max-Planck-Institut für Radioastronomie (MPIFR), Sydney Institute for Astronomy (SIfA), The University of Sydney, Department of Physics-Electronics, Rhodes University, Grahamstown, University of Edinburgh, Universität Hamburg (UHH), Leibniz-Institut für Astrophysik Potsdam (AIP), School of Physics and Astronomy [Southampton], University of Southampton, Onsala Space Observatory (OSO), Chalmers University of Technology [Göteborg], Radboud University [Nijmegen], Medstar Research Institute, Thüringer Landessternwarte Tautenburg (TLS), Hamburger Sternwarte/Hamburg Observatory, Joseph Louis LAGRANGE (LAGRANGE), Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Jodrell Bank Centre for Astrophysics, University of Manchester [Manchester], University of Amsterdam [Amsterdam] (UvA), Ruhr-Universität Bochum [Bochum], Oxford Astrophysics, University of Oxford, Karlsruhe Institute of Technology (KIT), Astronomical Institute Anton Pannekoek (AI PANNEKOEK), Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Universität Bielefeld, Kapteyn Astronomical Institute [Groningen], University of Groningen [Groningen], Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Argelander-Institut für Astronomie (AlfA), Rheinische Friedrich-Wilhelms-Universität Bonn, Observatoire de Paris - Site de Paris (OP), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Oonk, J.B.R., van Weeren, R.J., salgado, F., Morabito, L.K., Tielens, A.G.G.M., Rottgering, H.J.A., Asgekar, A., White, G.J., Alexov, A., Anderson, J., Avruch, I.M., Batejat, F., Beck, R., Be, M.E., van Bemmel, I., Bentum, M.J., Bernardi, G., Best, P., Bonafede, A., Breitling, F., Brentjens, M., Broderick, J., Brüggen, M., Butcher, H.R., Ciardi, B., Conway, J.E., Corstanje, A., de Gasperin, F., de Geus, E., de Vos, M., Duscha, S., Eislöffel, J., Engels, D., van Enst, J., Falcke, H., Fallows, R.A., Fender, R., Ferrari, C., Frieswijk, W., Garrett, M.A., Griemeier, J., Hamaker, J.P., Hassa, T.E., Heald, G., Hessels, J.W.T., Hoeft, M., Horneffer, A., van der Horst, A., Iacobelli, M., Jackson, N.J., Juette, E., Karastergiou, A., Klijn, W., Kohler, J., Kondratiev, V.I., Kramer, M., Kuniyoshi, M., Kuper, G., van Leeuwen, J., Maat, P., Macario, G., Mann, G., Markoff, S., McKean, J.P., Mevius, M., Miller-Jones, J.C.A., Mol, J.D., Mulcahy, D.D., Munk, H., Norden, M.J., Orru, E., Paas, H., Pandey-Pommier, M., Pandey, V.N., Pizzo, R., Polatidis, A.G., Reich, W., scaife, A.M.M., schoenmakers, A., schwarz, D., shulevski, A., sluman, J., smirnov, O., Sobey, C., Stappers, B.W., steinmetz, M., swinbank, J., Tagger, M., Tang, Y., Tasse, C., ter Veen, S., Thoudam, S., Toribio, C., van Nieuwpoort, R., Vermeulen, R., Vocks, C., Vogt, C., Wijers, R.A.M.J., Wise, M.W., Wucknitz, O., Yatawatta, S., Zarka, P., Zensus, A., Harvard University [Cambridge]-Smithsonian Institution, Universiteit Leiden [Leiden], Radboud university [Nijmegen], Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), University of Oxford [Oxford], École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Astronomy, and High Energy Astrophys. & Astropart. Phys (API, FNWI)
Subjects: [SDU.ASTR.CO]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], Astronomy, ISM: structure, Interstellar cloud, EWI-24499, FOS: Physical sciences, Astrophysics, structure-local interstellar matter-radio line, ISM [radio lines], Cygnus A, Absorption (electromagnetic radiation), Optical depth, Astrophysics::Galaxy Astrophysics, ISM, Line (formation), ISM: general, Physics, IsM, radio lines, radio lines: ISM, general [ISM], local interstellar matter, Local standard of rest, Astronomy and Astrophysics, METIS-302715, Astronomy and Astrophysic, Astrophysics - Astrophysics of Galaxies, Galaxy, Cassiopeia A, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, General-IsM, structure [ISM], IR-89519, ISM: general ISM: structure local interstellar matter radio lines: ISM
Abstract: We present the first detection of carbon radio recombination line absorption along the line of sight to Cygnus A. The observations were carried out with the LOw Frequency ARray in the 33 to 57 MHz range. These low frequency radio observations provide us with a new line of sight to study the diffuse, neutral gas in our Galaxy. To our knowledge this is the first time that foreground Milky Way recombination line absorption has been observed against a bright extragalactic background source. By stacking 48 carbon $\alpha$ lines in the observed frequency range we detect carbon absorption with a signal-to-noise ratio of about 5. The average carbon absorption has a peak optical depth of 2$\times$10$^{-4}$, a line width of 10 km s$^{-1}$ and a velocity of +4 km s$^{-1}$ with respect to the local standard of rest. The associated gas is found to have an electron temperature $T_{e}\sim$ 110 K and density $n_{e}\sim$ 0.06 cm$^{-3}$. These properties imply that the observed carbon $\alpha$ absorption likely arises in the cold neutral medium of the Orion arm of the Milky Way. Hydrogen and helium lines were not detected to a 3$\sigma$ peak optical depth limit of 1.5$\times$10$^{-4}$ for a 4 km s$^{-1}$ channel width. Radio recombination lines associated with Cygnus A itself were also searched for, but are not detected. We set a 3$\sigma$ upper limit of 1.5$\times$10$^{-4}$ for the peak optical depth of these lines for a 4 km s$^{-1}$ channel width., Comment: In press
Published: 2014

36. LOFAR tied-array imaging of Type III solar radio bursts

Author: Rene C. Vermeulen, John McKean, R. J. van Weeren, P. Maat, M. J. Norden, Gerard H. Kuper, Jean-Mathias Grießmeier, Sera Markoff, H. Paas, T. E. Hassall, V. I. Kondratiev, Jochen Eislöffel, Eoin P. Carley, A. G. Polatidis, A. A. Konovalenko, Hamish A. S. Reid, D. Engels, D. D. Mulcahy, Y. Tang, A. Nelles, Anna M. M. Scaife, A. Kerdraon, Oleg Smirnov, Olaf Wucknitz, Chiara Ferrari, Wolfgang Reich, Heino Falcke, Peter T. Gallagher, I. M. Avruch, Aris Karastergiou, Joel N. Bregman, H. Munk, Gianni Bernardi, Jörg R. Hörandel, Marcus Brüggen, Ashish Asgekar, F. de Gasperin, M. A. Garrett, W. Frieswijk, Marco Iacobelli, Pietro Zucca, E. de Geus, Sarod Yatawatta, Harvey Butcher, Diana E. Morosan, V. N. Pandey, Michel Tagger, Dominik J. Schwarz, Adam Stewart, M. Pandey-Pommier, E. Juette, Mark J. Bentum, Michael Kramer, A. W. Gunst, Emanuela Orru, S. Duscha, G. Pietka, H. O. Rucker, A. Horneffer, Philip Best, Matthias Hoeft, J. W. Broderick, C. Tasse, Gottfried Mann, R. Pizzo, James M. Anderson, M. Kuniyoshi, Ben Stappers, John Conway, Mario M. Bisi, Adam T. Deller, Christian Vocks, Alexander L. MacKinnon, Jasmina Magdalenic, Richard Fallows, Philippe Zarka, M. Serylak, Jason W. T. Hessels, Annalisa Bonafede, Benedetta Ciardi, C. Toribio, F. Breitling, Bo Thidé, H. J. A. Röttgering, Satyendra Thoudam, Morosan, D.E., Gallagher, P.T., Zucca, P., Fallows, R., Carley, E.P., Mann, G., Bisi, M.M., Kerdraon, A., Konovalenko, A.A., MacKinnon, A.L., Rucker, H.O., Thidé, B., Magdalenić, J., Vocks, C., Reid, H., Anderson, J., Asgekar, A., Avruch, I.M., Bentum, M.J., Bernardi, G., Best, P., Bonafede, A., Bregman, J., Breitling, F., Broderick, J., Brüggen, M., Butcher, H.R., Ciardi, B., Conway, J.E., De Gasperin, F., De Geus, E., Deller, A., Duscha, S., Eislöffel, J., Engels, D., Falcke, H., Ferrari, C., Frieswijk, W., Garrett, M.A., Grießmeier, J., Gunst, A.W., Hassall, T.E., Hessels, J.W.T., Hoeft, M., Hörandel, J., Horneffer, A., Iacobelli, M., Juette, E., Karastergiou, A., Kondratiev, V.I., Kramer, M., Kuniyoshi, M., Kuper, G., Maat, P., Markoff, S., McKean, J.P., Mulcahy, D.D., Munk, H., Nelles, A., Norden, M.J., Orru, E., Paas, H., Pandey-Pommier, M., Pandey, V.N., Pietka, G., Pizzo, R., Polatidis, A.G., Reich, W., Röttgering, H., Scaife, A.M.M., Schwarz, D., Serylak, M., Smirnov, O., Stappers, B.W., Stewart, A., Tagger, M., Tang, Y., Tasse, C., Thoudam, S., Toribio, C., Vermeulen, R., Van Weeren, R.J., Wucknitz, O., Yatawatta, S., Zarka, P., Trinity College Dublin, Leibniz-Institut für Astrophysik Potsdam (AIP), STFC Rutherford Appleton Laboratory (RAL), Science and Technology Facilities Council (STFC), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Institute of Radio Astronomy of NASU [Kharkiv] (IRA), National Academy of Sciences of Ukraine (NASU), Lawrence Livermore National Laboratory (LLNL), Space Research Institute of Austrian Academy of Sciences (IWF), Austrian Academy of Sciences (OeAW), Swedish Institute of Space Physics [Uppsala] (IRF), SRON Netherlands Institute for Space Research (SRON), Jacobs University [Bremen], University of Southampton, Research School of Astronomy and Astrophysics [Canberra] (RSAA), Australian National University (ANU), Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, Hamburger Sternwarte/Hamburg Observatory, Universität Hamburg (UHH), Netherlands Institute for Radio Astronomy (ASTRON), Thüringer Landessternwarte Tautenburg (TLS), Radboud University [Nijmegen], Joseph Louis LAGRANGE (LAGRANGE), Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Leiden Observatory [Leiden], Universiteit Leiden, Unité Scientifique de la Station de Nançay (USN), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Ruhr-Universität Bochum [Bochum], Max-Planck-Institut für Radioastronomie (MPIFR), Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Amsterdam [Amsterdam] (UvA), Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), National Radio Astronomy Observatory [Charlottesville] (NRAO), National Radio Astronomy Observatory (NRAO), School of Physics and Astronomy [Southampton], Laboratory for Atmospheric and Space Physics [Boulder] (LASP), University of Colorado [Boulder], Université Paris-Sud - Paris 11 (UP11), Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University-Smithsonian Institution, ANR-09-JCJC-0001,OPALES(2009), Kapteyn Astronomical Institute, Radboud university [Nijmegen], Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Universiteit Leiden [Leiden], Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Harvard University [Cambridge]-Smithsonian Institution, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Université Nice Sophia Antipolis (... - 2019) (UNS), Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Université d'Orléans (UO)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), PSL Research University (PSL)-PSL Research University (PSL)-Centre National d’Études Spatiales [Paris] (CNES), Smithsonian Institution-Harvard University [Cambridge], ANR-09-JCJC-0001,OPALES,nOn-thermal Processes in gALaxy cluStErs(2009), and High Energy Astrophys. & Astropart. Phys (API, FNWI)
Subjects: 010504 meteorology & atmospheric sciences, corona [Sun], Astronomy, WAVES, Astrophysics, particle emission [Sun], 01 natural sciences, CORONA, EWI-25429, Sun: coronal, Coronal mass ejection, Astrophysics::Solar and Stellar Astrophysics, GeneralLiterature_REFERENCE(e.g.,dictionaries,encyclopedias,glossaries), 010303 astronomy & astrophysics, Physics, Solar flare, Sun: radio radiation, [SDU.ASTR.HE]Sciences of the Universe [physics]/Astrophysics [astro-ph]/High Energy Astrophysical Phenomena [astro-ph.HE], ELECTRONS, Astrophysics - Solar and Stellar Astrophysics, Physical Sciences, IR-93233, Physics::Space Physics, SHOCK, Radio frequency, Astrophysics::Earth and Planetary Astrophysics, Sun: coronal mass ejections (CMEs), Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Solar radius, Astronomy & Astrophysics, ACCELERATION, Radio telescope, PLASMA EMISSION, SPACECRAFT, Sun: particle emission, 0103 physical sciences, Solar and Stellar Astrophysics (astro-ph.SR), 0105 earth and related environmental sciences, Science & Technology, RADIOHELIOGRAPH, radio radiation [Sun], [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Sun: corona, Astronomy and Astrophysics, LOFAR, METIS-309731, Astronomy and Astrophysic, Corona, coronal mass ejections (CMEs) [Sun], Space and Planetary Science, DENSITY, Temporal resolution, mass ejections (CMEs)
Abstract: The Sun is an active source of radio emission which is often associated with energetic phenomena such as solar flares and coronal mass ejections (CMEs). At low radio frequencies (, 9 pages, 6 figures
Published: 2014

37. Initial deep LOFAR observations of Epoch of Reionization windows: I. The North Celestial Pole

Author: M. A. Garrett, Vibor Jelić, Michel Tagger, B. Ciardi, Aris Karastergiou, Harish Vedantham, Marco Iacobelli, Michael W. Wise, Gianni Bernardi, Garrelt Mellema, F. Breitling, F. B. Abdalla, Panagiotis Labropoulos, H. Paas, R. J. van Weeren, Richard Fallows, Léon V. E. Koopmans, M. Kuniyoshi, Michiel A. Brentjens, W. N. Brouw, R. Nijboer, E. Juette, Emanuela Orru, Olaf Wucknitz, V. Veligatla, Gottfried Mann, Ben Stappers, John McKean, M. Mevius, A. G. Polatidis, J. M. Anderson, A. Alexov, Gerard H. Kuper, J. D. Mol, S. ter Veen, Annalisa Bonafede, R. Pizzo, A. W. Gunst, T. E. Hassall, M. Pandey-Pommier, Ph. Zarka, Joop Schaye, Geraint Harker, Michael Kramer, J. Sluman, P. Maat, Jason W. T. Hessels, M. J. Norden, H. J. A. Röttgering, A. R. Offringa, Philip Best, V. I. Kondratiev, Heino Falcke, V. N. Pandey, Chiara Ferrari, J. Noordam, S. Duscha, E. de Geus, John Conway, R. Vermeulen, Sarod Yatawatta, S. Kazemi, Matthias Hoeft, S. Daiboo, F. Batejat, Michael R. Bell, Wolfgang Reich, Saleem Zaroubi, J. M. Griessmeier, R. H. van de Brink, Rajat M. Thomas, Cyril Tasse, Y. Tang, J. W. Broderick, Emma Chapman, Mark J. Bentum, Stefan J. Wijnholds, J. van Leeuwen, Joel N. Bregman, H. Munk, Marcus Brüggen, F. de Gasperin, W. Frieswijk, I. M. Avruch, Oleg Smirnov, Matthias Steinmetz, Martin Bell, O. Martinez Rubi, de Antonius Bruyn, Netherlands Institute for Radio Astronomy (ASTRON), Kapteyn Astronomical Institute [Groningen], University of Groningen [Groningen], Department of process and energy, Delft University of Technology (TU Delft), Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University [Cambridge]-Smithsonian Institution, Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, Center for Astrophysics and Space Astronomy [Boulder] (CASA), University of Colorado [Boulder], Stockholm Observatory Department of Astronomy, Stockholm University, Leiden Observatory [Leiden], Universiteit Leiden [Leiden], Génétique Diversité et Ecophysiologie des Céréales (GDEC), Institut National de la Recherche Agronomique (INRA)-Université Blaise Pascal - Clermont-Ferrand 2 (UBP), University of Edinburgh, Jacobs University [Bremen], Leibniz-Institut für Astrophysik Potsdam (AIP), Onsala Space Observatory, Dept. of Radio and Space Science, Chalmers University of Technology, Chalmers University of Technology [Göteborg], Hamburger Sternwarte/Hamburg Observatory, Universität Hamburg (UHH), Medstar Research Institute, Max-Planck-Institut für Radioastronomie (MPIFR), Radboud university [Nijmegen], Joseph Louis LAGRANGE (LAGRANGE), Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Thüringer Landessternwarte Tautenburg (TLS), Ruhr-Universität Bochum [Bochum], Oxford Astrophysics, University of Oxford [Oxford], University of Amsterdam [Amsterdam] (UvA), Observatoire de Paris - Site de Meudon (OBSPM), Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Center for Information Technology CIT, Université de Groningen, Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Institut National de la Recherche Agronomique (INRA), Université Nice Sophia Antipolis (... - 2019) (UNS), Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Centre National d’Études Spatiales [Paris] (CNES), Yatawatta, S., De Bruyn, A.G., Brentjens, M.A., Labropoulos, P., Pandey, V.N., Kazemi, S., Zaroubi, S., Koopmans, L.V.E., Offringa, A.R., Jelić, V., Martinez Rubi, O., Veligatla, V., Wijnholds, S.J., Brouw, W.N., Bernardi, G., Ciardi, B., Daiboo, S., Harker, G., Mellema, G., Schaye, J., Thomas, R., Vedantham, H., Chapman, E., Abdalla, F.B., Alexov, A., Anderson, J., Avruch, I.M., Batejat, F., Bell, M.E., Bell, M.R., Bentum, M., Best, P., Bonafede, A., Bregman, J., Breitling, F., Van De Brink, R.H., Broderick, J.W., Brüggen, M., Conway, J., De Gasperin, F., De Geus, E., Duscha, S., Falcke, H., Fallows, R.A., Ferrari, C., Frieswijk, W., Garrett, M.A., Griessmeier, J.M., Gunst, A.W., Hassall, T.E., Hessels, J.W.T., Hoeft, M., Iacobelli, M., Juette, E., Karastergiou, A., Kondratiev, V.I., Kramer, M., Kuniyoshi, M., Kuper, G., Van Leeuwen, J., Maat, P., Mann, G., McKean, J.P., Mevius, M., Mol, J.D., Munk, H., Nijboer, R., Noordam, J.E., Norden, M.J., Orru, E., Paas, H., Pandey-Pommier, M., Pizzo, R., Polatidis, A.G., Reich, W., Röttgering, H.J.A., Sluman, J., Smirnov, O., Stappers, B., Steinmetz, M., Tagger, M., Tang, Y., Tasse, C., Ter Veen, S., Vermeulen, R., Van Weeren, R.J., Wise, M., Wucknitz, O., Zarka, P., High Energy Astrophys. & Astropart. Phys (API, FNWI), Harvard University-Smithsonian Institution, Universiteit Leiden, Radboud University [Nijmegen], Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), and University of Oxford
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO), Astronomy, first stars, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, 7. Clean energy, 01 natural sciences, Instrumentation: interferometer, METIS-302720, Celestial pole, first stars -instrumentation: interferometers -techniques: interferometric -methods: data analysis, 0103 physical sciences, dark ages, Instrumentation and Methods for Astrophysics (astro-ph.IM), 010303 astronomy & astrophysics, Reionization, Physics, reionization, instrumentation: interferometers, techniques: interferometric, methods: data analysis, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], 010308 nuclear & particles physics, IR-89500, Instrumentation: interferometers – Techniques: interferometric – Cosmology: observations, Astrophysics::Instrumentation and Methods for Astrophysics, EWI-24509, Astronomy and Astrophysics, LOFAR, Astronomy and Astrophysic, Redshift, Galaxy, diffuse radiation, Dark ages, reionization, first star, Orders of magnitude (time), Space and Planetary Science, Instrumentation: interferometers, Techniques: interferometric, ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, Ionosphere, Astrophysics - Instrumentation and Methods for Astrophysics, Noise (radio), Methods: data analysi, Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract: The aim of the LOFAR Epoch of Reionization (EoR) project is to detect the spectral fluctuations of the redshifted HI 21cm signal. This signal is weaker by several orders of magnitude than the astrophysical foreground signals and hence, in order to achieve this, very long integrations, accurate calibration for stations and ionosphere and reliable foreground removal are essential. One of the prospective observing windows for the LOFAR EoR project will be centered at the North Celestial Pole (NCP). We present results from observations of the NCP window using the LOFAR highband antenna (HBA) array in the frequency range 115 MHz to 163 MHz. The data were obtained in April 2011 during the commissioning phase of LOFAR. We used baselines up to about 30 km. With about 3 nights, of 6 hours each, effective integration we have achieved a noise level of about 100 microJy/PSF in the NCP window. Close to the NCP, the noise level increases to about 180 microJy/PSF, mainly due to additional contamination from unsubtracted nearby sources. We estimate that in our best night, we have reached a noise level only a factor of 1.4 above the thermal limit set by the noise from our Galaxy and the receivers. Our continuum images are several times deeper than have been achieved previously using the WSRT and GMRT arrays. We derive an analytical explanation for the excess noise that we believe to be mainly due to sources at large angular separation from the NCP., 19 pages, 24 figures. Draft version with low resolution images. Accepted on 08/01/2013 Astronomy & Astrophysics. Abstract abridged. Version with high resolution images: http://www.astro.rug.nl/~yatawatta/ncp_eor.pdf
Published: 2013

38. LOFAR detections of low-frequency radio recombination lines towards Cassiopeia A

Author: Jochen Eislöffel, Maaijke Mevius, R. J. van Weeren, Ralph A. M. J. Wijers, A. G. Polatidis, D. McKay-Bukowski, Chiara Ferrari, John Conway, Wilfred Frieswijk, Y. Tang, Glenn J. White, Robert Braun, Michael R. Bell, J. Sluman, W. A. van Cappellen, V. N. Pandey, Richard Fallows, Raffaella Morganti, H. J. A. Röttgering, Philip Best, M. A. Garrett, T. Grit, Charlotte Sobey, Emanuela Orrú, I. M. Avruch, P. Maat, M. J. Norden, Rainer Beck, D. D. Mulcahy, Michel Tagger, Annalisa Bonafede, James Miller-Jones, Aris Karastergiou, Sarod Yatawatta, J.-M. Grießmeier, J. B. R. Oonk, H. Paas, B. Ciardi, C. Tasse, Michael W. Wise, Heino Falcke, Gianni Bernardi, Ashish Asgekar, M. Kuniyoshi, Oleg Smirnov, Matthias Steinmetz, J. Kohler, Marco Iacobelli, E. Juette, John McKean, H. Munk, Marcus Brüggen, Harvey Butcher, G. Kuper, J. M. Anderson, V. I. Kondratiev, Christian Vocks, T. E. Hassall, M. Pandey-Pommier, Casey J. Law, F. Breitling, M. de Vos, A. W. Gunst, S. Duscha, Neal Jackson, Olaf Wucknitz, Sera Markoff, A. de Jong, Laura Birzan, Giulia Macario, A. Schoenmakers, Wolfgang Reich, Huib Intema, J. W. Broderick, J. D. Mol, E. de Geus, Jason W. T. Hessels, R. Pizzo, P. Zarka, George Heald, Mark J. Bentum, W. N. Brouw, Gottfried Mann, R. Vermeulen, Matthias Hoeft, F. Batejat, Bart Scheers, I. van Bemmel, Martin Bell, F. de Gasperin, J. van Leeuwen, R. H. van de Brink, Netherlands Institute for Radio Astronomy (ASTRON), Kapteyn Astronomical Institute [Groningen], University of Groningen [Groningen], Harvard-Smithsonian Center for Astrophysics (CfA), Smithsonian Institution-Harvard University [Cambridge], SLAC National Accelerator Laboratory (SLAC), Stanford University, Jodrell Bank Cent. for Astrophysics, University of Manchester [Manchester], Max-Planck-Institut für Radioastronomie (MPIFR), SRON Netherlands Institute for Space Research (SRON), Onsala Space Observatory (OSO), Chalmers University of Technology [Göteborg], Laboratoire de Chimie Physique Moléculaire (LCPM), Ecole Polytechnique Fédérale de Lausanne (EPFL), University of Southampton, Laboratoire de Physique Nucléaire et de Hautes Énergies (LPNHE), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Pierre et Marie Curie - Paris 6 (UPMC), University of Edinburgh, Leiden Observatory [Leiden], Universiteit Leiden [Leiden], Jacobs University [Bremen], Technische Universität Dresden = Dresden University of Technology (TU Dresden), Leibniz-Institut für Astrophysik Potsdam (AIP), Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, Hamburger Sternwarte/Hamburg Observatory, Universität Hamburg (UHH), Medstar Research Institute, Thüringer Landessternwarte Tautenburg (TLS), Radboud university [Nijmegen], Institute of Mathematical and Physical Sciences, Joseph Louis LAGRANGE (LAGRANGE), Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National d’Études Spatiales [Paris] (CNES), Unité Scientifique de la Station de Nançay (USN), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO), Jodrell Bank Centre for Astrophysics, University of Amsterdam [Amsterdam] (UvA), Dipartimento di Matematica 'Guido Castelnuovo' [Roma I] (Sapienza University of Rome), Università degli Studi di Roma 'La Sapienza' = Sapienza University [Rome], Centre de Mathématiques Laurent Schwartz (CMLS), Centre National de la Recherche Scientifique (CNRS)-École polytechnique (X), Ruhr-Universität Bochum [Bochum], Oxford Astrophysics, University of Oxford [Oxford], Karlsruhe Institute of Technology (KIT), Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Oulu, Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), National Radio Astronomy Observatory [Charlottesville] (NRAO), National Radio Astronomy Observatory (NRAO), Rhodes University, Grahamstown, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Argelander-Institut für Astronomie (AlfA), Rheinische Friedrich-Wilhelms-Universität Bonn, ANR-09-JCJC-0001,OPALES(2009), Harvard University-Smithsonian Institution, Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Universiteit Leiden, Radboud University [Nijmegen], Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Università degli Studi di Roma 'La Sapienza' = Sapienza University [Rome] (UNIROMA), École polytechnique (X)-Centre National de la Recherche Scientifique (CNRS), University of Oxford, École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Asgekar, A., Oonk, J.B.R., Yatawatta, S., Van Weeren, R.J., McKean, J.P., White, G., Jackson, N., Anderson, J., Avruch, I.M., Batejat, F., Beck, R., Bell, M.E., Bell, M.R., Van Bemmel, I., Bentum, M.J., Bernardi, G., Best, P., Bîrzan, L., Bonafede, A., Braun, R., Breitling, F., Van De Brink, R.H., Broderick, J., Brouw, W.N., Brüggen, M., Butcher, H.R., Van Cappellen, W., Ciardi, B., Conway, J.E., De Gasperin, F., De Geus, E., De Jong, A., De Vos, M., Duscha, S., Eislöffel, J., Falcke, H., Fallows, R.A., Ferrari, C., Frieswijk, W., Garrett, M.A., Grießmeier, J.-M., Grit, T., Gunst, A.W., Hassall, T.E., Heald, G., Hessels, J.W.T., Hoeft, M., Iacobelli, M., Intema, H., Juette, E., Karastergiou, A., Kohler, J., Kondratiev, V.I., Kuniyoshi, M., Kuper, G., Law, C., Van Leeuwen, J., Maat, P., MacArio, G., Mann, G., Markoff, S., McKay-Bukowski, D., Mevius, M., Miller-Jones, J.C.A., Mol, J.D., Morganti, R., Mulcahy, D.D., Munk, H., Norden, M.J., Orru, E., Paas, H., Pandey-Pommier, M., Pandey, V.N., Pizzo, R., Polatidis, A.G., Reich, W., Röttgering, H., Scheers, B., Schoenmakers, A., Sluman, J., Smirnov, O., Sobey, C., Steinmetz, M., Tagger, M., Tang, Y., Tasse, C., Vermeulen, R., Vocks, C., Wijers, R.A.M.J., Wise, M.W., Wucknitz, O., Zarka, P., High Energy Astrophys. & Astropart. Phys (API, FNWI), Astronomy, and Kapteyn Astronomical Institute
Subjects: Astronomy, chemistry.chemical_element, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, ISM: individual objects: Cassiopeia A, IR-89496, Astronomy & Astrophysics, Low frequency, ISM: individual objects: Cas siopeia A, 01 natural sciences, ISM: clouds, Spectral line, CARBON, MHZ, ISM: cloud, 0103 physical sciences, EWI-24495, Spectral resolution, Supernova remnant, 010303 astronomy & astrophysics, Helium, Radio lines: ISM, Astrophysics::Galaxy Astrophysics, Line (formation), Physics, radio lines : ISM, 010308 nuclear & particles physics, Astronomy and Astrophysics, LOFAR, Astronomy and Astrophysic, REGIONS, Astrophysics - Astrophysics of Galaxies, METIS-302711, Cassiopeia A, chemistry, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, ISM: clouds / radio lines: ISM / ISM: individual objects: Cassiopeia A, [SDU.ASTR.GA]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Galactic Astrophysics [astro-ph.GA]
Abstract: Cassiopeia A was observed using the Low-Band Antennas of the LOw Frequency ARray (LOFAR) with high spectral resolution. This allowed a search for radio recombination lines (RRLs) along the line-of-sight to this source. Five carbon-alpha RRLs were detected in absorption between 40 and 50 MHz with a signal-to-noise ratio of > 5 from two independent LOFAR datasets. The derived line velocities (v_LSR ~ -50 km/s) and integrated optical depths (~ 13 s^-1) of the RRLs in our spectra, extracted over the whole supernova remnant, are consistent within each LOFAR dataset and with those previously reported. For the first time, we are able to extract spectra against the brightest hotspot of the remnant at frequencies below 330 MHz. These spectra show significantly higher (15-80 %) integrated optical depths, indicating that there is small-scale angular structure on the order of ~1 pc in the absorbing gas distribution over the face of the remnant. We also place an upper limit of 3 x 10^-4 on the peak optical depths of hydrogen and helium RRLs. These results demonstrate that LOFAR has the desired spectral stability and sensitivity to study faint recombination lines in the decameter band., Accepted for publication in A&A Letters; 5 pages, 4 colour figures
Published: 2013

39. Detecting cosmic rays with the LOFAR radio telescope

Author: P. Maat, M. J. Norden, J. M. Anderson, N. J. Vermaas, E. de Geus, Sarod Yatawatta, Stefan J. Wijnholds, A. de Jong, J. D. Mol, Ben Stappers, C. Vogt, Philip Best, Pim Schellart, Stijn Buitink, D. McKay-Bukowski, M. Pandey-Pommier, Joel N. Bregman, H. Munk, Marcus Brüggen, Matthias Hoeft, P. Bennema, Jason W. T. Hessels, Charlotte Sobey, Benedetta Ciardi, M. de Vos, R.V. van Nieuwpoort, J. E. Enriquez, A. Alexov, R. J. van Weeren, S. Duscha, L. Bähren, Ph. Zarka, Aris Karastergiou, Gottfried Mann, Heino Falcke, Rene C. Vermeulen, V. I. Kondratiev, A. Horneffer, Michael W. Wise, Gianni Bernardi, R. Pizzo, D. D. Mulcahy, M. Kuniyoshi, Giulia Macario, Jörg R. Hörandel, Michael Kramer, Ralph A. M. J. Wijers, Richard Fallows, John McKean, Arthur Corstanje, Cyril Tasse, J. W. Broderick, A. H. W. M. Coolen, A. Nelles, George Heald, A. Zensus, A. Schoenmakers, John W. Romein, Michiel A. Brentjens, John D. Swinbank, C. Toribio, Jean-Mathias Grießmeier, Maria Krause, M. A. Garrett, Olaf Scholten, Dominik J. Schwarz, Y. Tang, M. van den Akker, T. E. Hassall, Oleg Smirnov, H. Paas, T. Grit, James Miller-Jones, R. Nijboer, Matthias Steinmetz, Marco Iacobelli, J. P. Hamaker, Emanuela Orru, C. W. James, J. van Leeuwen, J. Kohler, Chiara Ferrari, Christian Vocks, Jochen Eislöffel, Mark J. Bentum, Gerard H. Kuper, R. Overeem, A. G. Polatidis, I. M. Avruch, A. Renting, F. de Gasperin, W. Frieswijk, S. ter Veen, Martin Bell, E. Juette, Wouter Klijn, M. Mevius, Sera Markoff, H. A. Holties, Olaf Wucknitz, Rainer Beck, J. Sluman, H. J. A. Röttgering, Satyendra Thoudam, F. Breitling, High Energy Astrophys. & Astropart. Phys (API, FNWI), Radboud University [Nijmegen], SETI Institute, Netherlands Institute for Radio Astronomy (ASTRON), Max-Planck-Institut für Radioastronomie (MPIFR), Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, Erlangen Centre for Astroparticle Physics (ECAP), Friedrich-Alexander Universität Erlangen-Nürnberg (FAU), Max-Planck-Institut für Extraterrestrische Physik (MPE), Kernfysisch Versneller Instituut, Univ. of Groningen (KVI), University of Groningen [Groningen], Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), SRON Netherlands Institute for Space Research (SRON), Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Amsterdam [Amsterdam] (UvA), Laboratoire de Chimie Physique Moléculaire (LCPM), Ecole Polytechnique Fédérale de Lausanne (EPFL), Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University-Smithsonian Institution, University of Edinburgh, Leibniz-Institut für Astrophysik Potsdam (AIP), University of Southampton, Jacobs University [Bremen], London Institute for Mathematical Sciences, Hamburger Sternwarte/Hamburg Observatory, Universität Hamburg (UHH), Medstar Research Institute, Thüringer Landessternwarte Tautenburg (TLS), Institute of Mathematical and Physical Sciences, Joseph Louis LAGRANGE (LAGRANGE), Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Leiden Observatory [Leiden], Universiteit Leiden, Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Jodrell Bank Centre for Astrophysics, University of Manchester [Manchester], Ruhr-Universität Bochum [Bochum], Oxford Astrophysics, University of Oxford, Karlsruhe Institute of Technology (KIT), University of Oulu, Center for Agricultural Research in Suriname CELOS and Department of Biology, Anton de Kom Universiteit van Suriname - Anton de Kom University of Suriname [Paramaribo] (UVS), Center for Information Technology CIT, Université de Groningen, Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Interactions Son Musique Mouvement, Sciences et Technologies de la Musique et du Son (STMS), Institut de Recherche et Coordination Acoustique/Musique (IRCAM)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche et Coordination Acoustique/Musique (IRCAM)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), Rhodes University, Grahamstown, SKA South Africa, Ska South Africa, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Argelander-Institut für Astronomie (AlfA), Rheinische Friedrich-Wilhelms-Universität Bonn, Kapteyn Astronomical Institute [Groningen], ANR-09-JCJC-0001,OPALES(2009), European Project: 227610,EC:FP7:ERC,ERC-2008-AdG,LOFAR-AUGER(2009), Astronomy, Research unit Astroparticle Physics, Radboud university [Nijmegen], Harvard University [Cambridge]-Smithsonian Institution, Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Universiteit Leiden [Leiden], University of Oxford [Oxford], École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Université Nice Sophia Antipolis (... - 2019) (UNS), Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), PSL Research University (PSL)-PSL Research University (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Anton de Kom University of Suriname, Université Pierre et Marie Curie - Paris 6 (UPMC)-IRCAM-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-IRCAM-Centre National de la Recherche Scientifique (CNRS), Rhodes University, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), and ANR-09-JCJC-0001,OPALES,nOn-thermal Processes in gALaxy cluStErs(2009)
Subjects: EWI-24497, Astronomy, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Cosmic ray, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Low frequency, EXTENSIVE AIR-SHOWERS, 01 natural sciences, Electromagnetic interference, Radio telescope, CODALEMA, 0103 physical sciences, instrumentation: interferometers, 010303 astronomy & astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), Physics, High Energy Astrophysical Phenomena (astro-ph.HE), 010308 nuclear & particles physics, Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy and Astrophysics, LOFAR, METIS-302713, methods: data analysis, SIMULATIONS, PULSES, Interferometry, Space and Planetary Science, astroparticle physics, [SDU]Sciences of the Universe [physics], ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, ARRAY, astroparticle physics – methods: data analysis – instrumentation: interferometers, Antenna (radio), EMISSION, Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, Energy (signal processing), IR-89518
Abstract: International audience; The low frequency array (LOFAR), is the first radio telescope designed with the capability to measure radio emission from cosmic-ray induced air showers in parallel with interferometric observations. In the first $\sim 2\,\mathrm{years}$ of observing, 405 cosmic-ray events in the energy range of $10^{16} - 10^{18}\,\mathrm{eV}$ have been detected in the band from $30 - 80\,\mathrm{MHz}$. Each of these air showers is registered with up to $\sim1000$ independent antennas resulting in measurements of the radio emission with unprecedented detail. This article describes the dataset, as well as the analysis pipeline, and serves as a reference for future papers based on these data. All steps necessary to achieve a full reconstruction of the electric field at every antenna position are explained, including removal of radio frequency interference, correcting for the antenna response and identification of the pulsed signal.
Published: 2013

40. The brightness and spatial distributions of terrestrial radio sources

Author: W. N. Brouw, D. A. Rafferty, Oleg Smirnov, John McKean, Harvey Butcher, M. A. Garrett, M. Pandey-Pommier, Geraint Harker, Stefan J. Wijnholds, H. J. A. Röttgering, Marco Iacobelli, Jean-Mathias Grießmeier, Ashish Asgekar, Michael R. Bell, R. J. van Weeren, Abhik Ghosh, S. Duscha, Olaf Wucknitz, Christian Vocks, G. Kuper, Saleem Zaroubi, W. Reich, Frank Breitling, P. Maat, M. J. Norden, Ilian T. Iliev, I. M. Avruch, B. Ciardi, C. Tasse, Rene C. Vermeulen, Giulia Macario, Wilfred Frieswijk, V. I. Kondratiev, Chiara Ferrari, Rainer Beck, Laura Birzan, Y. Tang, Anna M. M. Scaife, Charlotte Sobey, S. ter Veen, A. Horneffer, M. Kuniyoshi, Emanuela Orrú, A. Alexov, Jochen Eislöffel, H. Paas, Luitje Koopmans, M. de Vos, E. Juette, Wouter Klijn, Michel Tagger, H. Meulman, A. G. Polatidis, F. B. Abdalla, J. van Leeuwen, J. Sluman, F. de Gasperin, A. R. Offringa, Roberto Pizzo, Richard Fallows, A. G. de Bruyn, Tim Hassall, R. van Nieuwpoort, Martin Bell, Mark J. Bentum, C. Toribio, J. W. Broderick, E. de Geus, M. Loose, Philippe Zarka, Philip Best, Marcus Brüggen, Gottfried Mann, J. M. Anderson, Aris Karastergiou, Michael W. Wise, Gianni Bernardi, Garrelt Mellema, Research School of Astronomy and Astrophysics [Canberra] (RSAA), Australian National University (ANU), Kapteyn Astronomical Institute [Groningen], University of Groningen [Groningen], Netherlands Institute for Radio Astronomy ( ASTRON ), University College of London [London] (UCL), Max-Planck-Institut für Astrophysik (MPA), Max-Planck-Gesellschaft, University of Sussex, Center for Astrophysics and Space Astronomy [Boulder] (CASA), University of Colorado [Boulder], AlbaNova University Center, Stockholm University, Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University [Cambridge]-Smithsonian Institution, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Space Telescope Science Institute (STSci), Max-Planck-Institut für Radioastronomie (MPIFR), SRON Netherlands Institute for Space Research (SRON), University of Edinburgh, Leiden Observatory [Leiden], Universiteit Leiden [Leiden], Leibniz-Institut für Astrophysik Potsdam (AIP), School of Physics and Astronomy [Southampton], University of Southampton, Universität Hamburg (UHH), Thüringer Landessternwarte Tautenburg (TLS), Joseph Louis LAGRANGE (LAGRANGE), Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Ruhr-Universität Bochum [Bochum], Oxford Astrophysics, University of Oxford [Oxford], University of Amsterdam [Amsterdam] (UvA), Center for Information Technology CIT, Université de Groningen, Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Department of Physics-Electronics, Rhodes University, Grahamstown, Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), Radboud university [Nijmegen], Astronomical Institute Anton Pannekoek (AI PANNEKOEK), Argelander-Institut für Astronomie (AlfA), Rheinische Friedrich-Wilhelms-Universität Bonn, Harvard University-Smithsonian Institution, Universiteit Leiden, Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), University of Oxford, École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Radboud University [Nijmegen], Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Université Nice Sophia Antipolis (... - 2019) (UNS), Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Centre National d’Études Spatiales [Paris] (CNES), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-École normale supérieure - Lyon (ENS Lyon), Rhodes University, Kapteyn Astronomical Institute, Astronomy, and High Energy Astrophys. & Astropart. Phys (API, FNWI)
Subjects: Brightness, IR-89516, Astronomy, radio continuum: general, 02 engineering and technology, Astrophysics, PROPAGATION, Interference (wave propagation), 01 natural sciences, Cosmology, 0202 electrical engineering, electronic engineering, information engineering, EWI-24493, dark ages, instrumentation: interferometers, 010303 astronomy & astrophysics, Physics, INTERFERENCE MITIGATION, Astrophysics::Instrumentation and Methods for Astrophysics, ASTRONOMY, Physics - Atmospheric and Oceanic Physics, techniques: interferometric, Dark Ages, ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, reionization, methods: observational, Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - Cosmology and Nongalactic Astrophysics, atmospheric effects, Cosmology and Nongalactic Astrophysics (astro-ph.CO), [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph], first stars, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, reionisation, 0103 physical sciences, dark ages, reionization, first stars, Visibility, Reionization, Instrumentation and Methods for Astrophysics (astro-ph.IM), EPOCH, [PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph], atmospheric effects – instrumentation: interferometers – methods: observational – techniques: interferometric – radio continuum: general – dark ages, 020206 networking & telecommunications, Astronomy and Astrophysics, LOFAR, Redshift, METIS-302710, Space and Planetary Science, Atmospheric and Oceanic Physics (physics.ao-ph), TELESCOPES
Abstract: Faint undetected sources of radio-frequency interference (RFI) might become visible in long radio observations when they are consistently present over time. Thereby, they might obstruct the detection of the weak astronomical signals of interest. This issue is especially important for Epoch of Reionisation (EoR) projects that try to detect the faint redshifted HI signals from the time of the earliest structures in the Universe. We explore the RFI situation at 30-163 MHz by studying brightness histograms of visibility data observed with LOFAR, similar to radio-source-count analyses that are used in cosmology. An empirical RFI distribution model is derived that allows the simulation of RFI in radio observations. The brightness histograms show an RFI distribution that follows a power-law distribution with an estimated exponent around -1.5. With several assumptions, this can be explained with a uniform distribution of terrestrial radio sources whose radiation follows existing propagation models. Extrapolation of the power law implies that the current LOFAR EoR observations should be severely RFI limited if the strength of RFI sources remains strong after time integration. This is in contrast with actual observations, which almost reach the thermal noise and are thought not to be limited by RFI. Therefore, we conclude that it is unlikely that there are undetected RFI sources that will become visible in long observations. Consequently, there is no indication that RFI will prevent an EoR detection with LOFAR., Accepted for publication in MNRAS
Published: 2013

41. The LOFAR radio environment

Author: R.-J. Dettmar, Steve Rawlings, Vibor Jelić, Benedetta Ciardi, Ben Stappers, Aris Karastergiou, Y. Tang, R. Pizzo, V. N. Pandey, A. Alexov, Michael W. Wise, Gianni Bernardi, J. Eisloeffel, J. Sluman, W. A. van Cappellen, Panagiotis Labropoulos, Garrelt Mellema, A. Schoenmakers, M. Mevius, John Conway, P. Maat, M. P. van Haarlem, Rainer Beck, G. van Diepen, M. J. Norden, Heino Falcke, A. W. Gunst, Sarod Yatawatta, R. Nijboer, V. Veligatla, Joop Schaye, J. M. Anderson, D. A. Rafferty, S. Daiboo, M. Kuniyoshi, Michael R. Bell, A. G. Polatidis, A. van Duin, H. Paas, Harish Vedantham, A. G. de Bruyn, V. I. Kondratiev, H. Meulman, A. van Ardenne, Harvey Butcher, J. D. Mol, Laura Birzan, M. Pandey, Michel Tagger, Michiel A. Brentjens, M. Gerbers, Jason W. T. Hessels, George Heald, Matthias Steinmetz, Rob Fender, Marcus Brüggen, Annalisa Bonafede, Gottfried Mann, Mark J. Bentum, Saleem Zaroubi, J. Noordam, Charlotte Sobey, John McKean, John D. Swinbank, Olaf Wucknitz, Gerard H. Kuper, Stefan J. Wijnholds, O. Martinez-Ruby, Léon V. E. Koopmans, Ph. Zarka, Philip Best, Ashish Asgekar, Y. Koopman, R. Vermeulen, A. R. Offringa, R. J. van Weeren, Matthias Hoeft, A. Horneffer, Huub Röttgering, M. Avruch, T. E. Hassall, Martin Bell, J. M. Griessmeier, Geraint Harker, M. de Vos, Ralph A. M. J. Wijers, Christian Vocks, W. Frieswijk, Wolfgang Reich, Oleg Smirnov, Cyril Tasse, J. W. Broderick, F. Breitling, S. Kazemi, J. van Leeuwen, Kapteyn Astronomical Institute [Groningen], University of Groningen [Groningen], Netherlands Institute for Radio Astronomy (ASTRON), Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, Department of process and energy, Delft University of Technology (TU Delft), National Radio Astronomy Observatory [Charlottesville] (NRAO), National Radio Astronomy Observatory (NRAO), Leiden Observatory [Leiden], Universiteit Leiden [Leiden], Observatoire de Paris, Université Paris sciences et lettres (PSL), Laboratoire de Chimie Physique Moléculaire (LCPM), Ecole Polytechnique Fédérale de Lausanne (EPFL), University of Southampton, Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University [Cambridge]-Smithsonian Institution, University of Edinburgh, Jacobs University [Bremen], Leibniz-Institut für Astrophysik Potsdam (AIP), Astronomisches Institut der Ruhr-Universität Bochum, Ruhr-Universität Bochum [Bochum], Max-Planck-Institut für Radioastronomie (MPIFR), Radboud university [Nijmegen], Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Jodrell Bank Centre for Astrophysics, University of Manchester [Manchester], University of Amsterdam [Amsterdam] (UvA), Thüringer Landessternwarte Tautenburg (TLS), Oxford Astrophysics, University of Oxford [Oxford], Center for Agricultural Research in Suriname CELOS and Department of Biology, Anton de Kom Universiteit van Suriname - Anton de Kom University of Suriname [Paramaribo] (UVS), Center for Information Technology CIT, Université de Groningen, Department of Astronomy and Astrophysics [PennState], Pennsylvania State University (Penn State), Penn State System-Penn State System, Rhodes University, Grahamstown, Astronomical Institute Anton Pannekoek (AI PANNEKOEK), Department of Reproduction and Development, Erasmus University Rotterdam, Argelander-Institut für Astronomie (AlfA), Rheinische Friedrich-Wilhelms-Universität Bonn, Offringa, A.R., De Bruyn, A.G., Zaroubi, S., Van Diepen, G., Martinez-Ruby, O., Labropoulos, P., Brentjens, M.A., Ciardi, B., Daiboo, S., Harker, G., Jelić, V., Kazemi, S., Koopmans, L.V.E., Mellema, G., Pandey, V.N., Pizzo, R.F., Schaye, J., Vedantham, H., Veligatla, V., Wijnholds, S.J., Yatawatta, S., Zarka, P., Alexov, A., Anderson, J., Asgekar, A., Avruch, M., Beck, R., Bell, M., Bell, M.R., Bentum, M., Bernardi, G., Best, P., Birzan, L., Bonafede, A., Breitling, F., Broderick, J.W., Brüggen, M., Butcher, H., Conway, J., De Vos, M., Dettmar, R.J., Eisloeffel, J., Falcke, H., Fender, R., Frieswijk, W., Gerbers, M., Griessmeier, J.M., Gunst, A.W., Hassall, T.E., Heald, G., Hessels, J., Hoeft, M., Horneffer, A., Karastergiou, A., Kondratiev, V., Koopman, Y., Kuniyoshi, M., Kuper, G., Maat, P., Mann, G., McKean, J., Meulman, H., Mevius, M., Mol, J.D., Nijboer, R., Noordam, J., Norden, M., Paas, H., Pandey, M., Pizzo, R., Polatidis, A., Rafferty, D., Rawlings, S., Reich, W., Röttgering, H.J.A., Schoenmakers, A.P., Sluman, J., Smirnov, O., Sobey, C., Stappers, B., Steinmetz, M., Swinbank, J., Tagger, M., Tang, Y., Tasse, C., Van Ardenne, A., Van Cappellen, W., Van Duin, A.P., Van Haarlem, M., Van Leeuwen, J., Van Weeren, R.J., Vermeulen, R., Vocks, C., Wijers, R.A.M.J., Wise, M., Wucknitz, O., UMR Peuplement Végétaux et Bioagresseurs en Milieu Tropical (UMR PVBMT - INRA), Institut National de la Recherche Agronomique (INRA), Observatoire de Paris - Site de Paris (OP), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Centre National d’Études Spatiales [Paris] (CNES), Anton de Kom University of Suriname, Rhodes University, SKA South Africa, Ska South Africa, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), university Rotterdam, Astronomy, Kapteyn Astronomical Institute, Peuplements végétaux et bioagresseurs en milieu tropical (UMR PVBMT), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut de Recherche pour le Développement (IRD)-Institut National de la Recherche Agronomique (INRA)-Université de La Réunion (UR), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National d’Études Spatiales [Paris] (CNES), and High Energy Astrophys. & Astropart. Phys (API, FNWI)
Subjects: Astronomy, instrumentation: interferometers, methods: data analysis, techniques: interferometric, telescopes, radio continuum: general, FOS: Physical sciences, RFI, 02 engineering and technology, Interference (wave propagation), 01 natural sciences, EWI-22636, Instrumentation: interferometer, Radio continuum: general, REMOVAL, Instrumentation: interferometers - Methods: data analysis - Techniques: interferometric - Telescopes - Radio continuum: general, 0103 physical sciences, Broadband, 0202 electrical engineering, electronic engineering, information engineering, Range (statistics), 010303 astronomy & astrophysics, IR-82457, Instrumentation and Methods for Astrophysics (astro-ph.IM), Telescope, FILTERING TECHNIQUES, Remote sensing, Significant difference, INTERFERENCE MITIGATION, Linearity, ASTRONOMY, 020206 networking & telecommunications, Astronomy and Astrophysics, Time resolution, LOFAR, Astronomy and Astrophysic, Space and Planetary Science, [SDU]Sciences of the Universe [physics], Techniques: interferometric, TELESCOPES, ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, Environmental science, Astrophysics - Instrumentation and Methods for Astrophysics, METIS-293223, Radio astronomy, Methods: data analysi
Abstract: Aims: This paper discusses the spectral occupancy for performing radio astronomy with the Low-Frequency Array (LOFAR), with a focus on imaging observations. Methods: We have analysed the radio-frequency interference (RFI) situation in two 24-h surveys with Dutch LOFAR stations, covering 30-78 MHz with low-band antennas and 115-163 MHz with high-band antennas. This is a subset of the full frequency range of LOFAR. The surveys have been observed with a 0.76 kHz / 1 s resolution. Results: We measured the RFI occupancy in the low and high frequency sets to be 1.8% and 3.2% respectively. These values are found to be representative values for the LOFAR radio environment. Between day and night, there is no significant difference in the radio environment. We find that lowering the current observational time and frequency resolutions of LOFAR results in a slight loss of flagging accuracy. At LOFAR's nominal resolution of 0.76 kHz and 1 s, the false-positives rate is about 0.5%. This rate increases approximately linearly when decreasing the data frequency resolution. Conclusions: Currently, by using an automated RFI detection strategy, the LOFAR radio environment poses no perceivable problems for sensitive observing. It remains to be seen if this is still true for very deep observations that integrate over tens of nights, but the situation looks promising. Reasons for the low impact of RFI are the high spectral and time resolution of LOFAR; accurate detection methods; strong filters and high receiver linearity; and the proximity of the antennas to the ground. We discuss some strategies that can be used once low-level RFI starts to become apparent. It is important that the frequency range of LOFAR remains free of broadband interference, such as DAB stations and windmills., Comment: Accepted for publication in A&A. 15 figures, 16 pages
Published: 2013

42. Corrigendum: A large light-mass component of cosmic rays at 1017–1017.5 electronvolts from radio observations

Author: Wilfred Frieswijk, M. P. van Haarlem, Anna M. M. Scaife, Vishambhar Pandey, M. C. Toribio, A. Horneffer, Michael Kramer, Jochen Eislöffel, S. ter Veen, Harvey Butcher, A. W. Gunst, J. van Leeuwen, Maaijke Mevius, G. van Diepen, E. de Geus, Sarod Yatawatta, Adam Stewart, Adam Deller, V. I. Kondratiev, M. Pandey-Pommier, Laura Rossetto, D. Carbone, A. Nelles, A. G. Polatidis, Tim Hassall, D. D. Mulcahy, James M. Anderson, S. Duscha, Ralph A. M. J. Wijers, J. Sluman, Roberto Pizzo, Marcus Brüggen, Rebecca McFadden, Hubertus Intema, E. Juette, Stijn Buitink, Satyendra Thoudam, Rob Fender, M. Serylak, R. C. Vermeulen, F. de Gasperin, Y. Tang, O. Scholten, Christian Vocks, J. W. Broderick, M. A. Garrett, P. Maat, M. J. Norden, John D. Swinbank, Heino Falcke, John McKean, H. J. A. Röttgering, Aris Karastergiou, Mark J. Bentum, M. Iacobelli, Arthur Corstanje, Sera Markoff, Benjamin Stappers, M. Tagger, Michael W. Wise, Gianni Bernardi, Jörg R. Hörandel, G. M. Loose, Dominik J. Schwarz, Martin Bell, C. Tasse, Frank Breitling, John Conway, Annalisa Bonafede, H. Paas, M. Steinmetz, Gottfried Mann, R. J. Dettmar, Stefan J. Wijnholds, George Heald, Jason W. T. Hessels, T. Huege, Oleg Smirnov, W. N. Brouw, P. Zarka, J.-M. Grießmeier, B. Ciardi, D. Engels, O. Wucknitz, J. E. Enriquez, M. Kuniyoshi, Richard Fallows, G. Kuper, W. Reich, M. Pietka, Emanuela Orrú, Ashish Asgekar, C. Vogt, Philip Best, Pim Schellart, J. P. Rachen, H. Munk, R. J. van Weeren, D. McKay-Bukowski, Chiara Ferrari, T. N. G. Trinh, Matthias Hoeft, J. A. Zensus, I. M. Avruch, Department of Astrophysics [Nijmegen], Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), Radboud university [Nijmegen]-Radboud university [Nijmegen], Radboud university [Nijmegen], Karlsruher Institut für Technologie (KIT), Institute for Mathematics Applied to Geoscience, National Center for Atmospheric Research [Boulder] (NCAR), Netherlands Institute for Radio Astronomy (ASTRON), SRON Netherlands Institute for Space Research (SRON), CSIRO Astronomy and Space Science, Commonwealth Scientific and Industrial Research Organisation [Canberra] (CSIRO), University of Edinburgh, Jacobs University [Bremen], Leibniz-Institut für Astrophysik Potsdam (AIP), University of Southampton, Kapteyn Astronomical Institute [Groningen], University of Groningen [Groningen], University of Amsterdam [Amsterdam] (UvA), Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, Medstar Research Institute, Astronomisches Institut der Ruhr-Universität Bochum, Ruhr-Universität Bochum [Bochum], Thüringer Landessternwarte Tautenburg (TLS), Hamburger Sternwarte/Hamburg Observatory, Universität Hamburg (UHH), Institut de Génomique Fonctionnelle de Lyon (IGFL), École normale supérieure - Lyon (ENS Lyon)-Institut National de la Recherche Agronomique (INRA)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS), Département de Géologie, Université de Montréal [Montréal], Leiden Observatory [Leiden], Universiteit Leiden [Leiden], Jodrell Bank Centre for Astrophysics, University of Manchester [Manchester], Rhodes University, Max-Planck-Institut für Radioastronomie (MPIFR), Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Oulu, Center for Information Technology CIT, Université de Groningen, Centre de Recherche Astrophysique de Lyon (CRAL), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-École normale supérieure - Lyon (ENS Lyon), Department of Physics and Astronomy [Ghent], Ghent University [Belgium] (UGENT), Oxford Astrophysics, University of Oxford [Oxford], School of Physics and Astronomy [Southampton], Interactions Son Musique Mouvement, Sciences et Technologies de la Musique et du Son (STMS), Université Pierre et Marie Curie - Paris 6 (UPMC)-IRCAM-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-IRCAM-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Centre National d’Études Spatiales [Paris] (CNES), Leibniz-Institut DSMZ-Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH / Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures (DSMZ), Laboratory for Atmospheric and Space Physics [Boulder] (LASP), University of Colorado [Boulder], Université Libre de Bruxelles [Bruxelles] (ULB), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Argelander-Institut für Astronomie (AlfA), Rheinische Friedrich-Wilhelms-Universität Bonn, Observatoire de Paris - Site de Paris (OP), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS), Radboud University [Nijmegen]-Radboud University [Nijmegen], Radboud University [Nijmegen], École normale supérieure de Lyon (ENS de Lyon)-Institut National de la Recherche Agronomique (INRA)-Université Claude Bernard Lyon 1 (UCBL), Université de Montréal (UdeM), Universiteit Leiden, Rhodes University, Grahamstown, École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Universiteit Gent = Ghent University (UGENT), University of Oxford, Institut de Recherche et Coordination Acoustique/Musique (IRCAM)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche et Coordination Acoustique/Musique (IRCAM)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Université libre de Bruxelles (ULB), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut National de la Recherche Agronomique (INRA)-École normale supérieure - Lyon (ENS Lyon), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Universiteit Gent = Ghent University [Belgium] (UGENT), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National d’Études Spatiales [Paris] (CNES)
Subjects: Pierre Auger Observatory, Astroparticle physics, Physics, [PHYS]Physics [physics], Multidisciplinary, 010504 meteorology & atmospheric sciences, High-energy astronomy, Astronomy, Electronvolt, Cosmic ray, LOFAR, Astrophysics, 01 natural sciences, Auger, International Cosmic Ray Conference, 0103 physical sciences, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], 010303 astronomy & astrophysics, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences
Abstract: In this Letter, we omitted to cite preliminary results from the low-energy extension of the Pierre Auger Observatory, as presented at the International Cosmic Ray Conference 2015 (ref. 1). Figure 1 of this Corrigendum shows measurements of the average value of Xmax for the Low Frequency Array (LOFAR), and earlier experiments using different techniques, now including the data from the Pierre Auger Observatory1 , specifically the contribution of A. Porcelli. Our values are in agreement with those of ref. 1 within systematic uncertainties.
Published: 2016

43. Observing pulsars and fast transients with LOFAR

Author: S. ter Veen, A. W. Gunst, John D. Swinbank, T. Grit, R.-J. Dettmar, Sera Markoff, Patrick Weltevrede, M. A. Garrett, J. Sluman, Léon V. E. Koopmans, P. Maat, George Heald, John McKean, J. P. Hamaker, M. J. Norden, H. J. A. Röttgering, Sarod Yatawatta, V. S. Dhillon, Aris Karastergiou, J. D. Mol, A. Noutsos, M. P. van Haarlem, C. G. M. Sterks, Y. Tang, Casey J. Law, Stefan J. Wijnholds, Ashish Asgekar, Jason W. T. Hessels, Jochen Eislöffel, W. N. Brouw, A. van Duin, P. Bennema, M. Gerbers, J. W. Broderick, V. I. Kondratiev, P. C. Broekema, Michael W. Wise, Harvey Butcher, A. Alexov, James Miller-Jones, Oleg Smirnov, H. Spreeuw, L. Bähren, M. Loose, Joel N. Bregman, J. Noordam, A. G. de Bruyn, Philippe Zarka, R. Vermeulen, A. G. Polatidis, Marcus Brüggen, Heino Falcke, Kenneth C. Anderson, Matthias Hoeft, Matthias Steinmetz, A. Zensus, H. A. Holties, M. Pandey-Pommier, A. Schoenmakers, Olaf Wucknitz, Gerard H. Kuper, C. Vogt, Michael Kramer, Hans Olofsson, Bart Scheers, J. M. Anderson, N. J. Vermaas, Philip Best, T. E. Hassall, B. W. Stappers, D. McKay-Bukowski, R. Nijboer, Rob Fender, Ralph A. M. J. Wijers, T. Coenen, M. de Vos, George K. Miley, Mark J. Bentum, Rainer Beck, R. H. van de Brink, John Conway, Wolfgang Reich, Michel Tagger, E. J. Daw, Martin Bell, I. M. Avruch, B. Ciardi, A. Horneffer, John W. Romein, J. van Enst, Michiel A. Brentjens, J. van Leeuwen, J. M. Griessmeier, Raffaella Morganti, Kapteyn Astronomical Institute, Astronomy, Jodrell Bank Centre for Astrophysics (JBCA), University of Manchester [Manchester], University of Amsterdam [Amsterdam] (UvA), Astronomical Institute Anton Pannekoek (AI PANNEKOEK), Oxford Astrophysics, University of Oxford [Oxford], Netherlands Institute for Radio Astronomy (ASTRON), Max-Planck-Institut für Radioastronomie (MPIFR), University of Southampton, University of Sheffield [Sheffield], Thüringer Landessternwarte Tautenburg (TLS), Unité Scientifique de la Station de Nançay (USN), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), Radboud university [Nijmegen], Argelander-Institut für Astronomie (AlfA), Rheinische Friedrich-Wilhelms-Universität Bonn, Observatoire de Paris - Site de Paris (OP), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), SRON Netherlands Institute for Space Research (SRON), Kapteyn Astronomical Institute [Groningen], University of Groningen [Groningen], Jacobs University [Bremen], Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, Astronomisches Institut der Ruhr-Universität Bochum, Ruhr-Universität Bochum [Bochum], Leiden Observatory [Leiden], Universiteit Leiden [Leiden], Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Netherlands Research School for Astronomy (Grant NOVA3-NW3-2.3.1), European Project: 224838,EC:FP7:PEOPLE,FP7-PEOPLE-2007-4-3-IRG,PULSARS WITH LOFAR(2008), University of Oxford, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Radboud University [Nijmegen], Universiteit Leiden, École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), and High Energy Astrophys. & Astropart. Phys (API, FNWI)
Subjects: DECAMETER WAVELENGTHS, Computer science, Astronomy, EWI-20531, INTENSITY VARIATIONS, 01 natural sciences, law.invention, FLUX DENSITIES, law, METIS-279184, instrumentation: interferometers, 010303 astronomy & astrophysics, GeneralLiterature_REFERENCE(e.g.,dictionaries,encyclopedias,glossaries), Astrophysics::Instrumentation and Methods for Astrophysics, INTERSTELLAR PLASMA, Astrophysics - Solar and Stellar Astrophysics, LOW-FREQUENCY, Radio frequency, Ionosphere, methods: observational, Astrophysics - Instrumentation and Methods for Astrophysics, Radio astronomy, Radio wave, BINARY MILLISECOND PULSAR, GAMMA-RAY PULSARS, NEUTRON-STARS, Astrophysics::High Energy Astrophysical Phenomena, IR-78088, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Low frequency, RADIO-CONTINUUM EMISSION, Radio telescope, Telescope, stars: neutron, Pulsar, pulsars: general, 0103 physical sciences, Instrumentation and Methods for Astrophysics (astro-ph.IM), Solar and Stellar Astrophysics (astro-ph.SR), ISM: general, 010308 nuclear & particles physics, Radio window, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Astronomy and Astrophysics, telescopes, LOFAR, [SDU.ASTR.IM]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM], Space and Planetary Science, DENSITY POWER SPECTRUM
Abstract: Low frequency radio waves, while challenging to observe, are a rich source of information about pulsars. The LOw Frequency ARray (LOFAR) is a new radio interferometer operating in the lowest 4 octaves of the ionospheric "radio window": 10-240MHz, that will greatly facilitate observing pulsars at low radio frequencies. Through the huge collecting area, long baselines, and flexible digital hardware, it is expected that LOFAR will revolutionize radio astronomy at the lowest frequencies visible from Earth. LOFAR is a next-generation radio telescope and a pathfinder to the Square Kilometre Array (SKA), in that it incorporates advanced multi-beaming techniques between thousands of individual elements. We discuss the motivation for low-frequency pulsar observations in general and the potential of LOFAR in addressing these science goals. We present LOFAR as it is designed to perform high-time-resolution observations of pulsars and other fast transients, and outline the various relevant observing modes and data reduction pipelines that are already or will soon be implemented to facilitate these observations. A number of results obtained from commissioning observations are presented to demonstrate the exciting potential of the telescope. This paper outlines the case for low frequency pulsar observations and is also intended to serve as a reference for upcoming pulsar/fast transient science papers with LOFAR., Comment: 35 pages, 19 figures, accepted for publication by A&A
Published: 2011

44. Lightning protection strategy used in LOFAR radio telescope

Author: M J Norden and J D Bregman
Published: 2010
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45. Differential frequency-dependent delay from the pulsar magnetosphere

Author: Jason W. T. Hessels, Tim Hassall, K. Zagkouris, Patrick Weltevrede, M. A. Garrett, Wilfred Frieswijk, F. de Gasperin, Y. Tang, P. Maat, Martin Bell, Jochen Eislöffel, R. Vermeulen, M. J. Norden, George Heald, Charlotte Sobey, F. Batejat, Chiara Ferrari, Jean-Mathias Griessmeier, James Miller-Jones, Ashish Asgekar, Mark J. Bentum, John McKean, Matthias Hoeft, Michael W. Wise, Gianni Bernardi, Heino Falcke, Michael Kramer, M. Pilia, R. J. van Weeren, M. Serylak, Annalisa Bonafede, C. Tasse, Harvey Butcher, Richard Fallows, J. W. Broderick, A. Alexov, J.-P. de Reijer, V. I. Kondratiev, P. Zarka, M. Pandey-Pommier, Stefan J. Wijnholds, E. Juette, A. W. Gunst, B. Ciardi, Philip Best, Rob Fender, A. Noutsos, Sarod Yatawatta, T. Coenen, H. J. A. Röttgering, M. Kuniyoshi, Ben Stappers, A. Karastergiou, W. Reich, A. G. Polatidis, Olaf Wucknitz, Evan Keane, S. Duscha, F. Breitling, J. Sluman, Roberto Pizzo, Marcus Brüggen, J. van Leeuwen, Hassall, T.E., Stappers, B.W., Weltevrede, P., Hessels, J.W.T., Alexov, A., Coenen, T., Karastergiou, A., Kramer, M., Keane, E.F., Kondratiev, V.I., Van Leeuwen, J., Noutsos, A., Pilia, M., Serylak, M., Sobey, C., Zagkouris, K., Fender, R., Bell, M.E., Broderick, J., Eislöffel, J., Falcke, H., Grießmeier, J.-M., Kuniyoshi, M., Miller-Jones, J.C.A., Wise, M.W., Wucknitz, O., Zarka, P., Asgekar, A., Batejat, F., Bentum, M.J., Bernardi, G., Best, P., Bonafede, A., Breitling, F., Brüggen, M., Butcher, H.R., Ciardi, B., De Gasperin, F., De Reijer, J.-P., Duscha, S., Fallows, R.A., Ferrari, C., Frieswijk, W., Garrett, M.A., Gunst, A.W., Heald, G., Hoeft, M., Juette, E., Maat, P., McKean, J.P., Norden, M.J., Pandey-Pommier, M., Pizzo, R., Polatidis, A.G., Reich, W., Röttgering, H., Sluman, J., Tang, Y., Tasse, C., Vermeulen, R., Van Weeren, R.J., Wijnholds, S.J., Yatawatta, S., High Energy Astrophys. & Astropart. Phys (API, FNWI), University of Southampton, Jodrell Bank Centre for Astrophysics, University of Manchester [Manchester], University of Amsterdam [Amsterdam] (UvA), Netherlands Institute for Radio Astronomy (ASTRON), Oxford Astrophysics, University of Oxford [Oxford], Max-Planck-Institut für Radioastronomie (MPIFR), Unité Scientifique de la Station de Nançay (USN), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Thüringer Landessternwarte Tautenburg (TLS), Radboud university [Nijmegen], Astronomical Institute Anton Pannekoek (AI PANNEKOEK), Argelander-Institut für Astronomie (AlfA), Rheinische Friedrich-Wilhelms-Universität Bonn, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Onsala Space Observatory (OSO), Chalmers University of Technology [Göteborg], Laboratoire de Physique Nucléaire et de Hautes Énergies (LPNHE), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Pierre et Marie Curie - Paris 6 (UPMC), University of Edinburgh, Jacobs University [Bremen], Leibniz-Institut für Astrophysik Potsdam (AIP), Universität Hamburg (UHH), Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, Kapteyn Astronomical Institute [Groningen], University of Groningen [Groningen], Joseph Louis LAGRANGE (LAGRANGE), Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Leiden Observatory [Leiden], Universiteit Leiden [Leiden], Ruhr-Universität Bochum [Bochum], Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), ANR-09-JCJC-0001,OPALES(2009), European Project: 224838,EC:FP7:PEOPLE,FP7-PEOPLE-2007-4-3-IRG,PULSARS WITH LOFAR(2008), European Project: 267697,EC:FP7:ERC,ERC-2010-AdG_20100224,4PI-SKY(2011), Astronomy, University of Oxford, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Radboud University [Nijmegen], Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Universiteit Leiden, École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), and Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)
Subjects: IR-89517, POLARIZATION, stellar magnetism, Astronomy, EWI-24496, Magnetosphere, FOS: Physical sciences, Astrophysics, 01 natural sciences, RADIO PULSARS, Pulsar, 0103 physical sciences, Differential (infinitesimal), 010303 astronomy & astrophysics, Telescope, Solar and Stellar Astrophysics (astro-ph.SR), Physics, High Energy Astrophysical Phenomena (astro-ph.HE), DRIFTING SUBPULSES, STABILITY, 010308 nuclear & particles physics, Oscillation, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Astronomy and Astrophysics, Observable, telescopes, LOFAR, PROFILES, Astronomy and Astrophysic, METIS-302712, Pulse (physics), Pulsars: individual: PSR B0809+74, MODEL, stellar pulsations, Pulsars: general, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, pulsars, stellar rotation, PSR B0809+74, RADIATION, Longitude, Astrophysics - High Energy Astrophysical Phenomena, EMISSION, stellar atmospheres
Abstract: Some radio pulsars show clear drifting subpulses, in which subpulses are seen to drift in pulse longitude in a systematic pattern. Here we examine how the drifting subpulses of PSR B0809+74 evolve with time and observing frequency. We show that the subpulse period (P3) is constant on timescales of days, months and years, and between 14-5100 MHz. Despite this, the shapes of the driftbands change radically with frequency. Previous studies have concluded that, while the subpulses appear to move through the pulse window approximately linearly at low frequencies (< 500 MHz), a discrete step of 180 degrees in subpulse phase is observed at higher frequencies (> 820 MHz) near to the peak of the average pulse profile. We use LOFAR, GMRT, GBT, WSRT and Effelsberg 100-m data to explore the frequency-dependence of this phase step. We show that the size of the subpulse phase step increases gradually, and is observable even at low frequencies. We attribute the subpulse phase step to the presence of two separate driftbands, whose relative arrival times vary with frequency - one driftband arriving 30 pulses earlier at 20 MHz than it does at 1380 MHz, whilst the other arrives simultaneously at all frequencies. The drifting pattern which is observed here cannot be explained by either the rotating carousel model or the surface oscillation model, and could provide new insight into the physical processes happening within the pulsar magnetosphere., 10 pages, 6 figures, accepted for publication in Astronomy and Astrophysics
Published: 2013

46. A controlled study of dawn simulation in subsyndromal winter depression

Author: David H. Avery and M. J. Norden
Subjects: Light therapy, Male, Sleep Wake Disorders, Light, media_common.quotation_subject, medicine.medical_treatment, Quality of sleep, Developmental psychology, parasitic diseases, medicine, Humans, Wakefulness, media_common, Psychiatric Status Rating Scales, fungi, Seasonal Affective Disorder, Middle Aged, Phototherapy, Psychiatry and Mental health, Mood, Cross-Sectional Studies, Social interest, Psychiatric status rating scales, Female, sense organs, Psychology, Dawn simulation, Vigilance (psychology), Demography
Abstract: In a randomized, cross-over design, 16 subjects with recurrent autumn-winter symptoms but without major depression were treated with 4 days of dawn simulation consisting of a gradually increasing illuminance over 45 min peaking at 100 lx (slow dawn) and with 4 days of a light rapidly increasing over a 4 s period to 100 lx (rapid dawn). The slow dawn was significantly better than both baseline and the rapid dawn in improving subjective measures of energy, mood, social interest, productivity, quality of sleep and quality of awakening.
Published: 1993

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