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133 results on '"S. ter Veen"'

1. Monte-carlo simulation of the effective lunar aperture for detection of ultra-high energy neutrinos with LOFAR

Author: G. K. Krampah, S. Buitink, J. D. Bray, A. Corstanje, M. Desmet, H. Falcke, B. M. Hare, J. R. Hörandel, T. Huege, V. B. Jhansi, N. Karastathis, K. Mulrey, P. Mitra, A. Nelles, H. Pandya, O. Scholten, S. ter Veen, S. Thoudam, and T. Winchen
Subjects: Astrophysics, QB460-466, Nuclear and particle physics. Atomic energy. Radioactivity, QC770-798
Abstract: Abstract Ultra-high-energy (UHE) cosmic neutrinos interacting with the Moon’s regolith generate particle showers that emit Askaryan radiation. This radiation can be observed from the Earth using ground-based radio telescopes like LOFAR. We simulate the effective detection aperture for UHE neutrinos hitting the Moon. Under the same assumptions, results from this work are in good agreement with previous analytic parameterizations and Monte Carlo codes. The dependence of the effective detection aperture on the observing parameters, such as observing frequency and minimum detection threshold, and lunar characteristics like surface topography have been studied. Using a Monte Carlo simulation, we find that the detectable neutrino energy threshold is lowered when we include a realistic treatment of the inelasticity, transmission coefficient, and surface roughness. Lunar surface roughness at large scales enhances the total aperture for higher observation frequencies ( $$\nu \ge 1~\textrm{GHz}$$ ν ≥ 1 GHz ) but has no significant effect on the LOFAR aperture. However, roughness at scales small compared to the wavelength reduces the aperture at all frequencies.
Published: 2023
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2. Searching for intra-cloud positive leaders in VHF

Author: O. Scholten, B. M. Hare, J. Dwyer, N. Liu, C. Sterpka, K. Mulrey, and S. Ter Veen
Subjects: Medicine, Science
Abstract: Abstract We have used the LOw-Frequency ARray (LOFAR) to search for the growing tip of an intra-cloud (IC) positive leader. Even with our most sensitive beamforming method, where we coherently add the signals of about 170 antenna pairs, we were not able to detect any emission from the tip. Instead, we put constraints on the emissivity of very-high frequency (VHF) radiation from the tip at 0.5 pJ/MHz at 60 MHz, integrated over 100 ns. The limit is independent on whether this emission is in the form of short pulses or continuously radiating. The non-observation of VHF radiation from intra-cloud positive leaders implies that they proceed in an extremely gradual process, which is in sharp contrast with the observations of other parts of a lightning discharge.
Published: 2023
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3. Small‐Scale Discharges Observed Near the Top of a Thunderstorm

Author: O. Scholten, B. M. Hare, J. Dwyer, N. Liu, C. Sterpka, J. Assink, H. Leijnse, and S. ter Veen
Subjects: Geophysics. Cosmic physics, QC801-809
Abstract: Abstract We have used the LOw‐Frequency ARray (LOFAR) to image a few lightning flashes during a particularly severe thunderstorm. The images show an exceptional amount of VHF activity at altitudes above 10 km. Much of this is in the form of small‐scale discharges, not exceeding a few hundred meter, occurring seemingly randomly around the centers of active storm cells. To emphasize the incidental nature of these small‐scale discharges or sparks we refer to them as “sparkles.” A detailed investigation shows evidence that these sparkles are indicative of positive leader channels and that they are equivalent to the needle activity seen around positive leader tracks at lower altitudes.
Published: 2023
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4. A distinct negative leader propagation mode

Author: O. Scholten, B. M. Hare, J. Dwyer, N. Liu, C. Sterpka, I. Kolmašová, O. Santolík, R. Lán, L. Uhlíř, S. Buitink, A. Corstanje, H. Falcke, T. Huege, J. R. Hörandel, G. K. Krampah, P. Mitra, K. Mulrey, A. Nelles, H. Pandya, J. P. Rachen, T. N. G. Trinh, S. ter Veen, S. Thoudam, and T. Winchen
Subjects: Medicine, Science
Abstract: Abstract The common phenomenon of lightning still harbors many secrets such as what are the conditions for lightning initiation and what is driving the discharge to propagate over several tens of kilometers through the atmosphere forming conducting ionized channels called leaders. Since lightning is an electric discharge phenomenon, there are positively and negatively charged leaders. In this work we report on measurements made with the LOFAR radio telescope, an instrument primarily build for radio-astronomy observations. It is observed that a negative leader rather suddenly changes, for a few milliseconds, into a mode where it radiates 100 times more VHF power than typical negative leaders after which it spawns a large number of more typical negative leaders. This mode occurs during the initial stage, soon after initiation, of all lightning flashes we have mapped (about 25). For some flashes this mode occurs also well after initiation and we show one case where it is triggered twice, some 100 ms apart. We postulate that this is indicative of a small (order of 5 km $$^2$$ 2 ) high charge pocket. Lightning thus appears to be initiated exclusively in the vicinity of such a small but dense charge pocket.
Published: 2021
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5. Timing Calibration and Windowing Technique Comparison for Lightning Mapping Arrays

Author: Brian M. Hare, Harald Edens, Paul Krehbiel, William Rison, O. Scholten, S. Buitink, A. Corstanje, H. Falcke, J. R. Hörandel, Tim Huege, G. K. Krampah, P. Mitra, K. Mulrey, Anna Nelles, Hershal Pandya, J. P. Rachen, S. Thoudam, T. N. Trinh, S. ter Veen, and Tobias Winchen
Subjects: Astronomy, QB1-991, Geology, QE1-996.5
Abstract: Abstract Since their introduction 22 years ago, lightning mapping arrays (LMA) have played a central role in the investigation of lightning physics. Even in recent years with the proliferation of digital interferometers and the introduction of the LOw Frequency ARray (LOFAR) radio telescope, LMAs still play an important role in lightning science. LMA networks use a simple windowing technique that records the highest pulse in either 80 μs or 10 μs fixed windows in order to apply a time‐of‐arrival location technique. In this work, we develop an LMA‐emulator that uses lightning data recorded by LOFAR to simulate an LMA, and we use it to test three new styles of pulse windowing. We show that they produce very similar results as the more traditional LMA windowing, implying that LMA lightning mapping results are relatively independent of windowing technique. In addition, each LMA station has its GPS‐conditioned clock. While the timing accuracy of GPS receivers has improved significantly over the years, they still significantly limit the timing measurements of the LMA. Recently, new time‐of‐arrival techniques have been introduced that can be used to self‐calibrate systematic offsets between different receiving stations. Applying this calibration technique to a set of data with 32 ns uncertainty, observed by the Colorado LMA, improves the timing uncertainty to 19 ns. This technique is not limited to LMAs and could be used to help calibrate future multi‐station lightning interferometers.
Published: 2021
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6. Testing afterglow models of FRB 200428 with early post-burst observations of SGR 1935 + 2154

Author: A J Cooper, A Rowlinson, R A M J Wijers, C Bassa, K Gourdji, J Hessels, A J van der Horst, V Kondratiev, D Michilli, Z Pleunis, T Shimwell, S ter Veen, and High Energy Astrophys. & Astropart. Phys (API, FNWI)
Subjects: fast radio bursts, High Energy Astrophysical Phenomena (astro-ph.HE), Space and Planetary Science, stars neutron, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, stars individual, stars magnetars, acceleration of particles, SGR1935 + 2154
Abstract: We present LOFAR imaging observations from the April/May 2020 active episode of magnetar SGR 1935+2154. We place the earliest radio limits on persistent emission following the low-luminosity fast radio burst FRB 200428 from the magnetar. We also perform an image-plane search for transient emission and find no radio flares during our observations. We examine post-FRB radio upper limits in the literature and find that all are consistent with the multi-wavelength afterglow predicted by the synchrotron maser shock model interpretation of FRB 200428. However, early optical observations appear to rule out the simple versions of the afterglow model with constant-density circumburst media. We show that these constraints may be mitigated by adapting the model for a wind-like environment, but only for a limited parameter range. In addition, we suggest that late-time non-thermal particle acceleration occurs within the afterglow model when the shock is no longer relativistic, which may prove vital for detecting afterglows from other Galactic FRBs. We also discuss future observing strategies for verifying either magnetospheric or maser shock FRB models via rapid radio observations of Galactic magnetars and nearby FRBs., Comment: Accepted for publication in MNRAS
Published: 2022

7. Characteristics of recoil leaders as observed by LOFAR

Author: B. M. Hare, O. Scholten, S. Buitink, J. R. Dwyer, N. Liu, C. Sterpka, and S. ter Veen
Subjects: Astronomy
Abstract: Contains fulltext : 289944.pdf (Publisher’s version ) (Open Access)
Published: 2023

8. LOFAR early-time search for coherent radio emission from short GRB 181123B

Author: A. J. van der Horst, Ralph A. M. J. Wijers, Antonia Rowlinson, S. ter Veen, G. E. Anderson, R. L. C. Starling, K. Gourdji, Timothy W. Shimwell, S. Mandhai, and High Energy Astrophys. & Astropart. Phys (API, FNWI)
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE), Physics, 010308 nuclear & particles physics, Astrophysics::High Energy Astrophysical Phenomena, Phase (waves), FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, LOFAR, Astrophysics::Cosmology and Extragalactic Astrophysics, Electromagnetic emission, Kilonova, 01 natural sciences, Black hole, Neutron star, Space and Planetary Science, 0103 physical sciences, Gamma-ray burst, Astrophysics - High Energy Astrophysical Phenomena, 010303 astronomy & astrophysics, Short duration, Astrophysics::Galaxy Astrophysics
Abstract: The mergers of two neutron stars are typically accompanied by broad-band electromagnetic emission from either a relativistic jet or a kilonova. It has also been long predicted that coherent radio emission will occur during the merger phase or from a newly formed neutron star remnant, however this emission has not been seen to date. This paper presents the deepest limits for this emission from a neutron star merger folowing triggered LOFAR observations of the short gamma-ray burst (SGRB) 181123B, starting 4.4 minutes after the GRB occurred. During the X-ray plateau phase, a signature of ongoing energy injection, we detect no radio emission to a 3$\sigma$ limit of 153 mJy at 144 MHz (image integration time of 136 seconds), which is significantly fainter than the predicted emission from a standard neutron star. At a redshift of 1.8, this corresponds to a luminosity of $2.5 \times 10^{44}$ erg s$^{-1}$. Snapshot images were made of the radio observation on a range of timescales, targeting short duration radio flashes similar to fast radio bursts (FRBs). No emission was detected in the snapshot images at the location of GRB 181123B enabling constraints to be placed on the prompt coherent radio emission model and emission predicted to occur when a neutron star collapses to form a black hole. At the putative host redshift of 1.8 for GRB 181123B, the non detection of the prompt radio emission is two orders of magnitude lower than expected for magnetic reconnection models for prompt GRB emission and no magnetar emission is expected., Comment: MNRAS Accepted, 11 pages, 6 figures
Published: 2021

9. Interferometric imaging of intensely radiating negative leaders

Author: O. Scholten, B. M. Hare, J. Dwyer, N. Liu, C. Sterpka, I. Kolmašová, O. Santolík, R. Lán, L. Uhlíř, S. Buitink, T. Huege, A. Nelles, S. ter Veen, Astronomy, Physics, and Astronomy and Astrophysics Research Group
Subjects: Physics - Atmospheric and Oceanic Physics, Astronomy, Atmospheric and Oceanic Physics (physics.ao-ph), FOS: Physical sciences, physics.ao-ph, ddc:530, Astrophysics - Instrumentation and Methods for Astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), astro-ph.IM
Abstract: Physical review / D 105(6), 062007 (2022). doi:10.1103/PhysRevD.105.062007, The common phenomenon of lightning still harbors many secrets and only recently a new propagation mode was observed for negative leaders. While propagating in this “intensely radiating negative leader” (IRNL) mode a negative leader emits 100 times more very-high frequency (VHF) and broadband radiation than a more normal negative leader. We have reported that this mode occurs soon after initiation of all lightning flashes we have mapped as well as sometimes long thereafter. Because of the profuse emission of VHF the leader structure is very difficult to image. In this work we report on measurements made with the LOFAR radio telescope, an instrument primarily built for radio-astronomy observations. For this reason, as part of the present work, we have refined our time resolved interferometric 3-dimensional (TRI-D) imaging to take into account the antenna function. The images from the TRI-D imager show that during an IRNL there is an ionization front with a diameter in excess of 500 m where strong corona bursts occur. This is very different from what is seen for a normal negative leader where the corona bursts happen at the tip, an area of typically 10 m in diameter. The observed massive ionization wave supports the idea that this mode is indicative of a dense charge pocket., Published by Inst., Melville, NY
Published: 2022
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10. The Spontaneous Nature of Lightning Initiation Revealed

Author: Olaf Scholten, Joseph R. Dwyer, A. Nelles, Ningyu Liu, C. Sterpka, Brian Hare, S. ter Veen, Stijn Buitink, Astronomy, and Physics
Subjects: Physics, Beamforming, business.industry, Astronomy, lightning initiation, LOFAR, Low frequency, interferometry, Lightning, Interferometry, Flash (photography), Geophysics, Optics, ddc:550, General Earth and Planetary Sciences, Radio interferometer, business, streamers
Abstract: Geophysical research letters 48(23), GL095511 (2021). doi:10.1029/2021GL095511, Here, we present new radio interferometer beamforming observations of lightning initiation using data from the Low-Frequency Array (LOFAR). We show that the first lightning source in the flash increases exponentially in intensity by two orders of magnitude in 15 ��s, while propagating 88 m away from the initiation location at a constant speed of 4.8 �� 0.1 �� 10$^6$ m/s. A second source replaces the first source at the initiation location, and subsequent propagation of the lightning leader follows. We interpret the first source to be a rapidly propagating and intensifying positive streamer discharge that subsequently produces a hot leader channel near the initiation point. How lightning initiates is one of the greatest unsolved problems in the atmospheric sciences, and these results shed light on this longstanding mystery., Published by Wiley, Hoboken, NJ
Published: 2021

11. A distinct negative leader propagation mode

Author: T. Huege, Ivana Kolmasova, Heino Falcke, Olaf Scholten, Ningyu Liu, A. Nelles, H. Pandya, Stijn Buitink, Katie Mulrey, Jörg P. Rachen, Jörg R. Hörandel, Arthur Corstanje, Joseph R. Dwyer, Radek Lan, C. Sterpka, Brian Hare, Luděk Uhlíř, Ondřej Santolík, Tobias Winchen, G. K. Krampah, S. ter Veen, Pragati Mitra, T. N. G. Trinh, Satyendra Thoudam, Astronomy, Research unit Astroparticle Physics, Physics, and Faculty of Sciences and Bioengineering Sciences
Subjects: Physics, Atmospheric dynamics, Multidisciplinary, 010504 meteorology & atmospheric sciences, Astronomy, Science, Mode (statistics), Natural hazards, LOFAR, 010501 environmental sciences, 010502 geochemistry & geophysics, Lightning, 01 natural sciences, Article, Radio telescope, Medicine, Electric discharge, ddc:530, ddc:600, 0105 earth and related environmental sciences
Abstract: Scientific reports 11, 16256 (2021). doi:10.1038/s41598-021-95433-5, The common phenomenon of lightning still harbors many secrets such as what are the conditions for lightning initiation and what is driving the discharge to propagate over several tens of kilometers through the atmosphere forming conducting ionized channels called leaders. Since lightning is an electric discharge phenomenon, there are positively and negatively charged leaders. In this work we report on measurements made with the LOFAR radio telescope, an instrument primarily build for radio-astronomy observations. It is observed that a negative leader rather suddenly changes, for a few milliseconds, into a mode where it radiates 100 times more VHF power than typical negative leaders after which it spawns a large number of more typical negative leaders. This mode occurs during the initial stage, soon after initiation, of all lightning flashes we have mapped (about 25). For some flashes this mode occurs also well after initiation and we show one case where it is triggered twice, some 100 ms apart. We postulate that this is indicative of a small (order of 5 km$^2$) high charge pocket. Lightning thus appears to be initiated exclusively in the vicinity of such a small but dense charge pocket., Published by Macmillan Publishers Limited, part of Springer Nature, [London]
Published: 2021

12. The relationship of lightning radio pulse amplitudes and source altitudes as observed by LOFAR

Author: A. Nelles, Arthur Corstanje, Heino Falcke, Brian Hare, Stijn Buitink, Katie Mulrey, H. Pandya, J. G. O. Machado, T. Huege, Olaf Scholten, Satyendra Thoudam, G. K. Krampah, Pragati Mitra, S. ter Veen, Tobias Winchen, T. N. G. Trinh, Jörg P. Rachen, Jörg R. Hörandel, Astronomy, Astronomy and Astrophysics Research Group, Physics, and Faculty of Sciences and Bioengineering Sciences
Subjects: Astronomy, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Cosmology and Extragalactic Astrophysics, Environmental Science (miscellaneous), radio astronomy, Atmosphere, Flash (photography), Altitude, ddc:550, ddc:530, Physics::Atmospheric and Oceanic Physics, amplitude, Physics, pulse detection, Astrophysics::Instrumentation and Methods for Astrophysics, LOFAR, Lightning, Pulse (physics), Amplitude, Physics::Space Physics, General Earth and Planetary Sciences, lightning, Radio astronomy, altitude
Abstract: Earth and Space Science 9(4), e2021EA001958 (2022). doi:10.1029/2021EA001958, When a lightning flash is propagating in the atmosphere it is known that especially the negative leaders emit a large number of very high frequency (VHF) radio pulses. It is thought that this is due to streamer activity at the tip of the growing negative leader. In this work, we have investigated the dependence of the strength of this VHF emission on the altitude of such emission for two lightning flashes as observed by the Low Frequency ARray (LOFAR) radio telescope. We find for these two flashes that the extracted amplitude distributions are consistent with a power-law, and that the amplitude of the radio emissions decreases very strongly with source altitude, by more than a factor of 2 from 1 km altitude up to 5 km altitude. In addition, we do not find any dependence on the extracted power-law with altitude, and that the extracted power-law slope has an average around 3, for both flashes., Published by American Geophysical Union, Malden, Mass.
Published: 2021

13. Depth of shower maximum and mass composition of cosmic rays from 50 PeV to 2 EeV measured with the LOFAR radio telescope

Author: G. K. Krampah, G. Trinh, Tobias Winchen, Brian Hare, S. ter Veen, Pragati Mitra, Arthur Corstanje, Anna Nelles, Stijn Buitink, Katie Mulrey, Heino Falcke, H. Pandya, Jörg P. Rachen, J. R. Hörandel, Satyendra Thoudam, T. Huege, Olaf Scholten, Astronomy, Physics, and Faculty of Sciences and Bioengineering Sciences
Subjects: mass spectrum [cosmic radiation], air, Astronomy, Astrophysics::High Energy Astrophysical Phenomena, Hadron, FOS: Physical sciences, Cosmic ray, helium, Astrophysics, 01 natural sciences, High Energy Physics - Experiment, Radio telescope, High Energy Physics - Experiment (hep-ex), 0103 physical sciences, ddc:530, 010306 general physics, Line (formation), astro-ph.HE, High Energy Astrophysical Phenomena (astro-ph.HE), Experiments in gravity, cosmology, cosmic rays, Physics, Pierre Auger Observatory, hep-ex, 010308 nuclear & particles physics, model [interaction], nucleus, Astrophysics::Instrumentation and Methods for Astrophysics, parametrization, LOFAR, tension, Auger, observatory, detector [radio wave], Air shower, 13. Climate action, hadronic [model], galaxy, Astrophysics - High Energy Astrophysical Phenomena, statistical, Energy (signal processing), atmosphere [showers]
Abstract: We present an updated cosmic-ray mass composition analysis in the energy range $10^{16.8}$ to $10^{18.3}$ eV from 334 air showers measured with the LOFAR radio telescope, and selected for minimal bias. In this energy range, the origin of cosmic rays is expected to shift from galactic to extragalactic sources. The analysis is based on an improved method to infer the depth of maximum $X_{\rm max}$ of extensive air showers from radio measurements and air shower simulations. We show results of the average and standard deviation of $X_{\rm max}$ versus primary energy, and analyze the $X_{\rm max}$-dataset at distribution level to estimate the cosmic ray mass composition. Our approach uses an unbinned maximum likelihood analysis, making use of existing parametrizations of $X_{\rm max}$-distributions per element. The analysis has been repeated for three main models of hadronic interactions. Results are consistent with a significant light-mass fraction, at best fit $23$ to $39$ $\%$ protons plus helium, depending on the choice of hadronic interaction model. The fraction of intermediate-mass nuclei dominates. This confirms earlier results from LOFAR, with systematic uncertainties on $X_{\rm max}$ now lowered to 7 to $9$ $\mathrm{g/cm^2}$. We find agreement in mass composition compared to results from Pierre Auger Observatory, within statistical and systematic uncertainties. However, in line with earlier LOFAR results, we find a slightly lower average $X_{\rm max}$. The values are in tension with those found at Pierre Auger Observatory, but agree with results from other cosmic ray observatories based in the Northern hemisphere., 24 pages, 14 figures. Accepted for publication in Phys. Rev. D
Published: 2021

14. The Initial Stage of Cloud Lightning Imaged in High Resolution

Author: Ondrej Santolik, Katharine Mulrey, A. Nelles, Luděk Uhlíř, S. ter Veen, Heino Falcke, Tobias Winchen, Arthur Corstanje, Olaf Scholten, H. Pandya, Tim Huege, C. Sterpka, Joseph R. Dwyer, G. K. Krampah, Radek Lan, Pragati Mitra, Brian Hare, A. Pel, Ivana Kolmasova, Satyendra Thoudam, T. N. G. Trinh, Jörg P. Rachen, Jörg R. Hörandel, Stijn Buitink, Physics, Faculty of Sciences and Bioengineering Sciences, Astronomy, and Research unit Astroparticle Physics
Subjects: Atmospheric Science, 010504 meteorology & atmospheric sciences, business.industry, Astronomy, FOS: Physical sciences, High resolution, Cloud computing, LOFAR, 01 natural sciences, Lightning, Physics - Atmospheric and Oceanic Physics, Geophysics, 13. Climate action, Space and Planetary Science, Atmospheric and Oceanic Physics (physics.ao-ph), Earth and Planetary Sciences (miscellaneous), ddc:550, Stage (hydrology), business, Astrophysics - Instrumentation and Methods for Astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), Geology, 0105 earth and related environmental sciences, Remote sensing
Abstract: With LOFAR we have been able to image the development of lightning flashes with meter-scale accuracy and unprecedented detail. We discuss the primary steps behind our most recent lightning mapping method. To demonstrate the capabilities of our technique we show and interpret images of the first few milliseconds of two intra-cloud flashes. In all our flashes the negative leaders propagate in the charge layer below the main negative charge. Among several interesting features we show that in about 2~ms after initiation the Primary Initial Leader triggers the formation of a multitude (more than ten) negative leaders in a rather confined area of the atmosphere. From these only one or two continue to propagate after about 30~ms to extend over kilometers horizontally while another may propagate back to the initiation point. We also show that normal negative leaders can transition into an initial-leader like state, potentially in the presence of strong electric fields. In addition, we show some initial breakdown pulses that occurred during the primary initial leader, and even during two "secondary" initial leaders that developed out of stepped leaders., Submitted to Journal of geophysics research: Atmospheres
Published: 2021

15. Multifrequency observations of SGR J1935+2154

Author: Marc Klein-Wolt, A. Addis, K. Gourdji, A. Possenti, Mateusz Malenta, M. Serylak, Elmar Körding, Mitchell B. Mickaliger, A. J. Cooper, Jason W. T. Hessels, Alessio Magro, Ramesh Karuppusamy, M. Geyer, D. J. Champion, C. G. Bassa, Giovanni Naldi, S. ter Veen, Kaustubh Rajwade, G. Desvignes, Vanessa McBride, Kerry Paterson, Laura Spitler, Germano Bianchi, Laura Driessen, Aditya Parthasarathy, Gianni Bernardi, Fabian Jankowski, Ralph A. M. J. Wijers, Patrick Woudt, Mayuresh Surnis, Benetge Perera, Marco Tavani, V. Venkatraman Krishnan, Marcus E. Lower, Antonia Rowlinson, Michael Kramer, V. I. Kondratiev, Vincent Morello, M. Caleb, Benjamin Stappers, Giancarlo Setti, Matthew Bailes, Mechiel Christiaan Bezuidenhout, Ian Heywood, Paul J. Groot, R. S. Le Poole, Weiwei Chen, M. Burgay, Giuseppe Pupillo, S. Buchner, Steven Bloemen, Ziggy Pleunis, Andrew Lyne, Kang Liu, Maura Pilia, P. M. Vreeswijk, D. L. A. Pieterse, ITA, GBR, AUS, High Energy Astrophys. & Astropart. Phys (API, FNWI), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, and 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)
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE), Physics, 010308 nuclear & particles physics, Astronomy, FOS: Physical sciences, Astronomy and Astrophysics, LOFAR, Astrophysics, Magnetar, Astrophysics - high energy astrophysical phenomena, 01 natural sciences, Optical telescope, law.invention, Telescope, Radio telescope, 13. Climate action, Space and Planetary Science, law, 0103 physical sciences, Stars: magnetars, Optical emission spectroscopy, Fast radio bursts, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], 010303 astronomy & astrophysics
Abstract: Magnetars are a promising candidate for the origin of Fast Radio Bursts (FRBs). The detection of an extremely luminous radio burst from the Galactic magnetar SGR J1935+2154 on 2020 April 28 added credence to this hypothesis. We report on simultaneous and non-simultaneous observing campaigns using the Arecibo, Effelsberg, LOFAR, MeerKAT, MK2 and Northern Cross radio telescopes and the MeerLICHT optical telescope in the days and months after the April 28 event. We did not detect any significant single radio pulses down to fluence limits between 25 mJy ms and 18 Jy ms. Some observing epochs overlapped with times when X-ray bursts were detected. Radio images made on four days using the MeerKAT telescope revealed no point-like persistent or transient emission at the location of the magnetar. No transient or persistent optical emission was detected over seven days. Using the multi-colour MeerLICHT images combined with relations between DM, NH and reddening we constrain the distance to SGR J1935+2154, to be between 1.5 and 6.5 kpc. The upper limit is consistent with some other distance indicators and suggests that the April 28 burst is closer to two orders of magnitude less energetic than the least energetic FRBs. The lack of single-pulse radio detections shows that the single pulses detected over a range of fluences are either rare, or highly clustered, or both. It may also indicate that the magnetar lies somewhere between being radio-quiet and radio-loud in terms of its ability to produce radio emission efficiently., Comment: Accepted for publication in MNRAS. Corresponding author B. W. Stappers
Published: 2021

16. Time resolved 3D interferometric imaging of a section of a negative leader with LOFAR

Author: Brian Hare, S. ter Veen, Ningyu Liu, C. Sterpka, Joseph R. Dwyer, Stijn Buitink, T. Huege, Olaf Scholten, A. Nelles, Astronomy, and Physics
Subjects: Beamforming, 010504 meteorology & atmospheric sciences, Astronomy, FOS: Physical sciences, physics.ao-ph, Low frequency, 01 natural sciences, Optics, 0103 physical sciences, ddc:530, Instrumentation and Methods for Astrophysics (astro-ph.IM), 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Physics, business.industry, LOFAR, Lightning, Corona, Interferometry, Physics - Atmospheric and Oceanic Physics, Orders of magnitude (time), Atmospheric and Oceanic Physics (physics.ao-ph), Thunderstorm, business, Astrophysics - Instrumentation and Methods for Astrophysics, astro-ph.IM
Abstract: Physical review / D 104(6), 063022 (2021). doi:10.1103/PhysRevD.104.063022, We have developed a three dimensional interferometric beamforming technique for imaging lightning flashes using very-high frequency (VHF) radio data recorded from several hundred antennas with baselines up to 100 km as offered by the Low Frequency Array. The long baselines allow us to distinguish fine structures on the scale of meters, while the large number of antennas allow us to observe processes that radiate at the same intensity as the background when using a time resolution that is close to the impulse-response time of the system, 100 ns. The new beamforming imaging technique is complementary to our existing impulsive imaging technique. We apply this new tool to the imaging of four stepped negative leaders in two flashes. For one flash, we observe the dynamics of corona bursts that are emitted in the stepping process. Additionally, we show that the intensity emitted in VHF during the stepping process follows a power law over 4 orders of magnitude in intensity for four leaders in two different lightning storms., Published by Inst., Melville, NY
Published: 2021

17. Distinguishing features of high altitude negative leaders as observed with LOFAR

Author: Joseph R. Dwyer, G. K. Krampah, C. Sterpka, A. Nelles, Arthur Corstanje, Heino Falcke, Stijn Buitink, Katie Mulrey, S. ter Veen, Ningyu Liu, H. Pandya, T. N. G. Trinh, Jörg P. Rachen, Jörg R. Hörandel, Tobias Winchen, Pragati Mitra, Satyendra Thoudam, Brian Hare, T. Huege, Olaf Scholten, Physics, Faculty of Sciences and Bioengineering Sciences, and Astronomy
Subjects: Atmospheric Science, 010504 meteorology & atmospheric sciences, Astronomy, Physics, High resolution, LOFAR, 010501 environmental sciences, Effects of high altitude on humans, 01 natural sciences, Thunderstorms, Lightning, Negative leaders, Radio telescope, Altitude, Corona flash, ddc:530, Radio emission, LOFAR lightning imaging, Geology, 0105 earth and related environmental sciences
Abstract: Atmospheric research 260, 105688 (2021). doi:10.1016/j.atmosres.2021.105688, We present high resolution observations of negative leaders at high altitude using the LOFAR radio telescope. We show that the structure of negative leaders at high altitude (altitudes larger than 7 km) differs in several respects from that of negative leaders at lower altitudes. In particular, the High Altitude Negative Leaders (HANLs) show very distinct steps of a few hundred meters, stepping times of the order of a few milliseconds and a filamentary structure that extends outward over several hundreds of meters; as opposed to lower altitude (�� 5 km) leaders, which have stepping times and distances around 0.01 ms and 10 m. Similar to lower altitude leaders, high altitude leaders emit copious VHF radiation from their propagating tip and have propagation velocities of the order of 10$^5$ m/s. Corona-flash like bursts can be distinguished when zooming in to meter and nanosecond scales., Published by Elsevier, Amsterdam [u.a.]
Published: 2021

18. Needle Propagation and Twinkling Characteristics

Author: Arthur Corstanje, C. Strepka, Brian Hare, Jörg P. Rachen, Jörg R. Hörandel, T. Huege, Olaf Scholten, Tobias Winchen, Heino Falcke, G. K. Krampah, H. Pandya, Satyendra Thoudam, Pragati Mitra, Joseph R. Dwyer, A. Nelles, Stijn Buitink, Katie Mulrey, S. ter Veen, T. N. G. Trinh, Astronomy, Physics, and Faculty of Sciences and Bioengineering Sciences
Subjects: Physics, Atmospheric Science, business.industry, Astronomy, imaging, LOFAR, needles, Lightning, VHF, Geophysics, Optics, Recoil, Space and Planetary Science, ddc:550, Earth and Planetary Sciences (miscellaneous), ddc:530, mapping, business, lightning, Twinkling
Abstract: Journal of geophysical research / D 126(6), JD034252 (2021). doi:10.1029/2020JD034252, Recently, a new lightning phenomena, termed needles, has been observed in both VHF and in optical along positive lightning leaders. They appear as small (, Published by Wiley, Hoboken, NJ
Published: 2021

19. Reconstructing air shower parameters with LOFAR using event specific GDAS atmosphere

Author: Brian Hare, Anna Nelles, Stijn Buitink, Katie Mulrey, Heino Falcke, S. ter Veen, T. N. G. Trinh, Laura Rossetto, H. Pandya, Jörg P. Rachen, G. K. Krampah, Antonio Bonardi, Tim Huege, Jörg R. Hörandel, Pragati Mitra, Arthur Corstanje, Olaf Scholten, Tobias Winchen, Faculty of Sciences and Bioengineering Sciences, Physics, Elementary Particle Physics, Astronomy, and Research unit Astroparticle Physics
Subjects: Meteorology, Effects of humidity, Astronomy, Astrophysics::High Energy Astrophysical Phenomena, Monte Carlo method, FOS: Physical sciences, Cosmic ray, Atmospheric model, 01 natural sciences, Cosmic Ray, Atmosphere, Data assimilation, 0103 physical sciences, Instrumentation and Methods for Astrophysics (astro-ph.IM), 010303 astronomy & astrophysics, Physics::Atmospheric and Oceanic Physics, astro-ph.HE, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, Atmospheric models, Radio detection technique, 010308 nuclear & particles physics, Astrophysics::Instrumentation and Methods for Astrophysics, Index of refraction, X-max reconstruction, Astronomy and Astrophysics, LOFAR, EAS, GDAS, COSMIC-RAYS, Air shower, 13. Climate action, RADIO-EMISSION, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Instrumentation and Methods for Astrophysics, astro-ph.IM
Abstract: The limited knowledge of atmospheric parameters like humidity, pressure, temperature, and the index of refraction has been one of the important systematic uncertainties in reconstructing the depth of the shower maximum from the radio emission of air showers. Current air shower Monte Carlo simulation codes like CORSIKA and the radio plug-in CoREAS use various averaged parameterized atmospheres. However, time-dependent and location-specific atmospheric models are needed for the cosmic ray analysis method used for LOFAR data. There, dedicated simulation sets are used for each detected cosmic ray, to take into account the actual atmospheric conditions at the time of the measurement. Using the Global Data Assimilation System (GDAS), a global atmospheric model, we have implemented time-dependent, realistic atmospheric profiles in CORSIKA and CoREAS. We have produced realistic event-specific atmospheres for all air showers measured with LOFAR, an event set spanning several years and many different weather conditions. A complete re-analysis of our data set shows that for the majority of data, our previous correction factor performed rather well; we found only a small systematic shift of 2 g/cm$^2$ in the reconstructed $X_{\rm max}$. However, under extreme weather conditions, for example, very low air pressure, the shift can be up to 15 g/cm$^2$. We provide a correction formula to determine the shift in $X_{\rm max}$ resulting from a comparison of simulations done using the US-Std atmosphere and the GDAS-based atmosphere., Comment: Accepted for publication in Astroparticle Physics. arXiv admin note: text overlap with arXiv:1911.02859
Published: 2020

20. Radio Emission Reveals Inner Meter-Scale Structure of Negative Lightning Leader Steps

Author: Heino Falcke, G. K. Krampah, B. Neijzen, H. Pandya, Joseph R. Dwyer, Jörg P. Rachen, Arthur Corstanje, Brian Hare, Ute Ebert, Antonio Bonardi, Tim Huege, Jörg R. Hörandel, Tobias Winchen, S Sander Nijdam, Olaf Scholten, Stijn Buitink, Katie Mulrey, S. ter Veen, Laura Rossetto, T. N. G. Trinh, Pragati Mitra, A. Nelles, Elementary Processes in Gas Discharges, Astronomy, Research unit Astroparticle Physics, and Centrum Wiskunde & Informatica, Amsterdam (CWI), The Netherlands
Subjects: Physics, Astronomy, STREAMERS, General Physics and Astronomy, Plasma, Astrophysics, LOFAR, Low frequency, Radiation, 01 natural sciences, Lightning, Corona, 13. Climate action, INCEPTION, 0103 physical sciences, Thunderstorm, Metre, ddc:530, 010306 general physics
Abstract: We use the Low Frequency Array (LOFAR) to probe the dynamics of the stepping process of negatively charged plasma channels (negative leaders) in a lightning discharge. We observe that at each step of a leader, multiple pulses of vhf (30-80 MHz) radiation are emitted in short-duration bursts (
Published: 2020

21. 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

22. A LOFAR census of non-recycled pulsars: extending to frequencies below 80 MHz

Author: Michael Kramer, Patrick Weltevrede, J. van Leeuwen, Charlotte Sobey, J.-M. Grießmeier, V. I. Kondratiev, Benjamin Stappers, Jason W. T. Hessels, Anna V. Bilous, S. ter Veen, Gilles Theureau, L. Bondonneau, High Energy Astrophys. & Astropart. Phys (API, FNWI), Institute of Interdisciplinary Studies, 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), 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), Laboratoire Univers et Théories (LUTH (UMR_8102)), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)
Subjects: Physics, [PHYS]Physics [physics], 010308 nuclear & particles physics, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Instrumentation and Methods for Astrophysics, Flux, Astronomy and Astrophysics, LOFAR, Astrophysics, 01 natural sciences, Pulsar, Space and Planetary Science, [SDU]Sciences of the Universe [physics], pulsars: general, 0103 physical sciences, [PHYS.PHYS.PHYS-INS-DET]Physics [physics]/Physics [physics]/Instrumentation and Detectors [physics.ins-det], [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], 010303 astronomy & astrophysics
Abstract: International audience; We present the results from the low-frequency (40–78 MHz) extension of the first pulsar census of non-recycled pulsars carried out with the LOw-Frequency ARray (LOFAR). We used the low-band antennas of the LOFAR core stations to observe 87 pulsars out of 158 that had been previously detected using high-band antennas. We present flux densities and flux-calibrated profiles for the 43 pulsars we detected. Of this sample, 17 have not, to our knowledge, previously been detected at such low frequencies. Here we recalculate the spectral indices using the new low-frequency flux density measurements from the LOFAR census and discuss the prospects of studying pulsars at very low frequencies using current and upcoming facilities, such as the New Extension in Nançay Upgrading LOFAR (NenuFAR).Key words: pulsars: general⋆ The profiles are also available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/635/A75
Published: 2020

23. On the cosmic-ray energy scale of the LOFAR radio telescope

Author: Arthur Corstanje, A. Nelles, Katharine Mulrey, Brian Hare, Tobias Winchen, G. K. Krampah, Satyendra Thoudam, Tim Huege, Jörg P. Rachen, Olaf Scholten, Pragati Mitra, S. ter Veen, Stijn Buitink, T. N. G. Trinh, Jörg R. Hörandel, Heino Falcke, H. Pandya, Physics, Faculty of Sciences and Bioengineering Sciences, Elementary Particle Physics, and Astronomy
Subjects: detector [cosmic radiation], air, Astronomy, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, magnetic field, Cosmic ray, 7. Clean energy, 01 natural sciences, Electromagnetic radiation, Radio telescope, energy [cosmic radiation], electromagnetic [energy], 0103 physical sciences, plastics [scintillation counter], ddc:530, energy [radiation], Instrumentation and Methods for Astrophysics (astro-ph.IM), High Energy Astrophysical Phenomena (astro-ph.HE), astro-ph.HE, Pierre Auger Observatory, Physics, 010308 nuclear & particles physics, Astrophysics::Instrumentation and Methods for Astrophysics, Radiant energy, Astronomy and Astrophysics, LOFAR, calibration, Auger, Computational physics, observatory, detector [radio wave], Air shower, Antenna (radio), Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Instrumentation and Methods for Astrophysics, Energy (signal processing), astro-ph.IM, atmosphere [showers]
Abstract: Cosmic rays are routinely measured at LOFAR, both with a dense array of antennas and with the LOFAR Radboud air shower Array (LORA) which is an array of plastic scintillators. In this paper, we present two results relating to the cosmic-ray energy scale of LOFAR. First, we present the reconstruction of cosmic-ray energy using radio and particle techniques along with a discussion of the event-by-event and absolute scale uncertainties. The resulting energies reconstructed with each method are shown to be in good agreement, and because the radio-based reconstructed energy has smaller uncertainty on an event-to-event basis, LOFAR analyses will use that technique in the future. Second, we present the radiation energy of air showers measured at LOFAR and demonstrate how radiation energy can be used to compare the energy scales of different experiments. The radiation energy scales quadratically with the electromagnetic energy in an air shower, which can in turn be related to the energy of the primary particle. Once the local magnetic field is accounted for, the radiation energy allows for a direct comparison between the LORA particle-based energy scale and that of the Pierre Auger Observatory. They are shown to agree to within (6$\pm$20)% for a radiation energy of 1 MeV, where the uncertainty on the comparison is dominated by the antenna calibrations of each experiment. This study motivates the development of a portable radio array which will be used to cross-calibrate the energy scales of different experiments using radiation energy and the same antennas, thereby significantly reducing the uncertainty on the comparison.
Published: 2020

24. LOFAR 144-MHz follow-up observations of GW170817

Author: Oleg Smirnov, Martin J. Hardcastle, P. Zarka, Adam Stewart, H. Paas, D. Carbone, P. Maat, Dominik J. Schwarz, M. C. Toribio, David A. Nichols, G. Mann, Rudy Wijnands, A. J. van der Horst, Evan Keane, H. J. A. Röttgering, Olaf Wucknitz, C. Tasse, T. Muñoz-Darias, Henk Mulder, M. H. D. van der Wiel, Kenta Hotokezaka, M. P. van Haarlem, Stephane Corbel, J. B. R. Oonk, S. ter Veen, A. W. Gunst, W. N. Brouw, Casey J. Law, M. Iacobelli, K. Gourdji, Samaya Nissanke, J. W. Broderick, Timothy W. Shimwell, R. Pekal, Rob Fender, W. Reich, James M. Anderson, Matthias Hoeft, Anna Nelles, R. Blaauw, Luitje Koopmans, J. van Leeuwen, Aleksandar Shulevski, R. J. van Weeren, Pietro Zucca, Marian Soida, Martin Bell, Ralph A. M. J. Wijers, Vanessa A. Moss, M. Pandey-Pommier, Thomas M. O. Franzen, Antonia Rowlinson, Anjali A. A. Piette, S. Duscha, Richard Fallows, M. A. Garrett, Peter G. Jonker, Mark J. Bentum, J.-M. Grießmeier, M. de Vos, B. Ciardi, Jörg R. Hörandel, E. Jütte, C. Vocks, M. Serylak, Andrzej Krankowski, Marcus Brüggen, Jochen Eislöffel, M. Pietka, 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)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), 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), 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), 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), 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), High Energy Astrophys. & Astropart. Phys (API, FNWI), Astroparticle Physics (IHEF, IoP, FNWI), 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), 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), Laboratoire de physique et chimie de l'environnement (LPCE), Université d'Orléans (UO)-Institut national des sciences de l'Univers (INSU - CNRS)-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), Astronomy, and Kapteyn Astronomical Institute
Subjects: Astronomy, FOS: Physical sciences, Binary number, Astrophysics, Astronomy & Astrophysics, 01 natural sciences, Radio spectrum, stars: neutron, neutron [stars], 0201 Astronomical and Space Sciences, 0103 physical sciences, 14. Life underwater, Center frequency, 010306 general physics, stars [radio continuum], 010303 astronomy & astrophysics, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, [PHYS]Physics [physics], Spectral index, Gravitational wave, Astronomy and Astrophysics, LOFAR, Afterglow, Neutron star, gravitational waves, Space and Planetary Science, ddc:520, Astrophysics - High Energy Astrophysical Phenomena, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], radio continuum: stars
Abstract: We present low-radio-frequency follow-up observations of AT 2017gfo, the electromagnetic counterpart of GW170817, which was the first binary neutron star merger to be detected by Advanced LIGO-Virgo. These data, with a central frequency of 144 MHz, were obtained with LOFAR, the Low-Frequency Array. The maximum elevation of the target is just 13.7 degrees when observed with LOFAR, making our observations particularly challenging to calibrate and significantly limiting the achievable sensitivity. On time-scales of 130-138 and 371-374 days after the merger event, we obtain 3$\sigma$ upper limits for the afterglow component of 6.6 and 19.5 mJy beam$^{-1}$, respectively. Using our best upper limit and previously published, contemporaneous higher-frequency radio data, we place a limit on any potential steepening of the radio spectrum between 610 and 144 MHz: the two-point spectral index $\alpha^{610}_{144} \gtrsim -2.5$. We also show that LOFAR can detect the afterglows of future binary neutron star merger events occurring at more favourable elevations., Comment: 9 pages, 2 figures, accepted for publication in MNRAS
Published: 2020

25. Properties of the Lunar Detection Mode for ZeV-Scale Particles with LOFAR

Author: Anna Nelles, Arthur Corstanje, Olaf Scholten, Heino Falcke, Tobias Winchen, A. Hörandel, Pragati Mitra, T. N. G. Trinh, Brian Hare, Antonio Bonardi, Satyendra Thoudam, Jörg P. Rachen, S. ter Veen, Laura Rossetto, Stijn Buitink, Katie Mulrey, Pim Schellart, Astronomy and Astrophysics Research Group, Physics, and Faculty of Sciences and Bioengineering Sciences
Subjects: Physics, 010308 nuclear & particles physics, Astronomy, Astrophysics::High Energy Astrophysical Phenomena, QC1-999, Detector, Mode (statistics), Astrophysics::Instrumentation and Methods for Astrophysics, Flux, Cosmic ray, LOFAR, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Physics::Geophysics, Radio telescope, Particle shower, 0103 physical sciences, Astrophysics::Earth and Planetary Astrophysics, 010303 astronomy & astrophysics, Energy (signal processing)
Abstract: The steep decrease of the flux of ultra-high energy cosmic rays (UHECR) provides a challenge to answer the long standing question about their origin and nature. A significant increase in detector volume may be achieved byemploying Earth’s moon as a detector that is read out using existing Earth-bound radio telescopes by searching for the radio pulses emitted by the particle shower in the lunar rock. In this contribution we will report on the properties of a corresponding detection mode currently under development for the LOFAR Radio telescope.
Published: 2019

26. The mass composition of cosmic rays measured with LOFAR

Author: Pim Schellart, Stijn Buitink, Katie Mulrey, Anna Nelles, Satyendra Thoudam, Tobias Winchen, Heino Falcke, Arthur Corstanje, T. N. G. Trinh, Jörg P. Rachen, S. ter Veen, Jörg R. Hörandel, Laura Rossetto, Olaf Scholten, Antonio Bonardi, Pragati Mitra, and Research unit Astroparticle Physics
Subjects: Physics::Instrumentation and Detectors, Astronomy, QC1-999, Astrophysics::High Energy Astrophysical Phenomena, Cosmic ray, Astrophysics::Cosmology and Extragalactic Astrophysics, Electron, Astrophysics, 01 natural sciences, law.invention, Atmosphere, law, 0103 physical sciences, Ultra-high-energy cosmic ray, GeneralLiterature_REFERENCE(e.g.,dictionaries,encyclopedias,glossaries), 010303 astronomy & astrophysics, Physics::Atmospheric and Oceanic Physics, Astroparticle physics, Physics, PAMELA detector, 010308 nuclear & particles physics, Astrophysics::Instrumentation and Methods for Astrophysics, LOFAR, Air shower, High Energy Physics::Experiment
Abstract: High-energy cosmic rays, impinging on the atmosphere of the Earth initiate cascades of secondary particles, the extensive air showers. The electrons and positrons in the air shower emit electromagnetic radiation. This emission is detected with the LOFAR radio telescope in the frequency range from 30 to 240 MHz. The data are used to determine the properties of the incoming cosmic rays. The radio technique is now routinely used to measure the arrival direction, the energy, and the particle type (atomic mass) of cosmic rays in the energy range from 1017 to 1018 eV. This energy region is of particular astrophysical interest, since in this regime a transition from a Galactic to an extra-galactic origin of cosmic rays is expected. For illustration, the LOFAR results are used to set constraints on models to describe the origin of high-energy cosmic rays.
Published: 2017

27. Updated Calibration of the LOFAR Low-Band Antennas

Author: Heino Falcke, T.N.G. Trinh, Arthur Corstanje, Tobias Winchen, Pim Schellart, Brian Hare, Satyendra Thoudam, J. P. Rachen, Stijn Buitink, Katie Mulrey, S. ter Veen, Jörg R. Hörandel, Laura Rossetto, Anna Nelles, Olaf Scholten, Pragati Mitra, Antonio Bonardi, Astronomy and Astrophysics Research Group, Physics, and Faculty of Sciences and Bioengineering Sciences
Subjects: Physics, 010308 nuclear & particles physics, QC1-999, Astronomy, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Instrumentation and Methods for Astrophysics, LOFAR, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Signal chain, Frequency spectrum, law.invention, Telescope, Air shower, law, 0103 physical sciences, Range (statistics), Calibration, 010306 general physics, Energy (signal processing), Remote sensing
Abstract: The LOw-Frequency ARray (LOFAR) telescope measures radio emission from air showers. In order to interpret the data, an absolute, frequency dependent calibration is required. Due to a growing need for a better understanding of the measured frequency spectrum, we revisit the calibration of the LOFAR antennas in the range of 30—80 MHz. Using the galactic radio emission and a detailed model of the LOFAR signal chain, we find a calibration that provides an absolute energy scale and allows us to study frequency dependent features in measured air shower signals.
Published: 2019

28. Cosmic Ray Physics with the LOFAR Radio Telescope

Author: Tobias Winchen, Anna Nelles, Katharine Mulrey, Jörg R. Hörandel, Heino Falcke, T. N. G. Trinh, Stijn Buitink, Brian Hare, Pragati Mitra, Arthur Corstanje, Jörg P. Rachen, Satyendra Thoudam, S. ter Veen, Laura Rossetto, Pim Schellart, A. Bonardi, Olaf Scholten, Physics, Astronomy and Astrophysics Research Group, Faculty of Sciences and Bioengineering Sciences, Elementary Particle Physics, and Faculty of Economic and Social Sciences and Solvay Business School
Subjects: History, Precision testing, Astronomy, Astrophysics::High Energy Astrophysical Phenomena, Measure (physics), FOS: Physical sciences, Cosmic ray, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Education, Radio telescope, 0103 physical sciences, 010303 astronomy & astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), Astrophysics::Galaxy Astrophysics, Astroparticle physics, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), astro-ph.HE, 010308 nuclear & particles physics, Astrophysics::Instrumentation and Methods for Astrophysics, LOFAR, Computer Science Applications, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Instrumentation and Methods for Astrophysics, astro-ph.IM
Abstract: The LOFAR radio telescope is able to measure the radio emission from cosmic ray induced air showers with hundreds of individual antennas. This allows for precision testing of the emission mechanisms for the radio signal as well as determination of the depth of shower maximum $X_{\max}$, the shower observable most sensitive to the mass of the primary cosmic ray, to better than 20 g/cm$^2$. With a densely instrumented circular area of roughly 320 m$^2$, LOFAR is targeting for cosmic ray astrophysics in the energy range $10^{16}$ - $10^{18}$ eV. In this contribution we give an overview of the status, recent results, and future plans of cosmic ray detection with the LOFAR radio telescope., Comment: Proceedings of the 26th Extended European Cosmic Ray Symposium (ECRS), Barnaul/Belokurikha, 2018
Published: 2019

29. 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

30. The LOFAR Tied-Array All-Sky Survey (LOTAAS): Survey overview and initial pulsar discoveries

Author: V. I. Kondratiev, Charlotte Sobey, Emanuela Orrú, M. C. Toribio, Benjamin Stappers, J. van Leeuwen, Roberto Pizzo, Richard Fallows, Aleksandar Shulevski, C. G. Bassa, S. Sanidas, Daniele Michilli, Aris Karastergiou, S. ter Veen, Pietro Zucca, C. M. Tan, M. Iacobelli, J.-M. Grießmeier, Michael Kramer, L. Cerrigone, S. Cooper, L. Bondonneau, Jason W. T. Hessels, Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Amsterdam [Amsterdam] (UvA), Jodrell Bank Centre for Astrophysics (JBCA), University of Manchester [Manchester], Netherlands Institute for Radio Astronomy (ASTRON), Dipartimento di Matematica 'Guido Castelnuovo' [Roma I] (Sapienza University of Rome), Università degli Studi di Roma 'La Sapienza' = Sapienza University [Rome], 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), 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), Oxford Astrophysics, University of Oxford [Oxford], Max-Planck-Institut für Radioastronomie (MPIFR), CNRS-INSU, France Observatoire de Paris, France, European Project: 337062,EC:FP7:ERC,ERC-2013-StG,DRAGNET(2014), European Project: 617199,EC:FP7:ERC,ERC-2013-CoG,ALERT(2014), High Energy Astrophys. & Astropart. Phys (API, FNWI), Università degli Studi di Roma 'La Sapienza' = Sapienza University [Rome] (UNIROMA), Radboud University [Nijmegen], Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), and University of Oxford
Subjects: media_common.quotation_subject, Astrophysics::High Energy Astrophysical Phenomena, Population, general [Pulsars], FOS: Physical sciences, Flux, Binary number, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Radio telescope, Pulsar, Millisecond pulsar, pulsars: general, 0103 physical sciences, observational [Methods], data analysis [Methods], education, 010303 astronomy & astrophysics, media_common, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, [PHYS]Physics [physics], education.field_of_study, 010308 nuclear & particles physics, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy and Astrophysics, LOFAR, methods: data analysis, Space and Planetary Science, Sky, methods: observational, Astrophysics - High Energy Astrophysical Phenomena, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract: We present an overview of the LOFAR Tied-Array All-Sky Survey (LOTAAS) for radio pulsars and fast transients. The survey uses the high-band antennas of the LOFAR Superterp, the dense inner part of the LOFAR core, to survey the northern sky (dec > 0 deg) at a central observing frequency of 135 MHz. A total of 219 tied-array beams (coherent summation of station signals, covering 12 square degrees), as well as three incoherent beams (covering 67 square degrees) are formed in each survey pointing. For each ofthe 222 beams, total intensity is recorded at 491.52 us time resolution. Each observation integrates for 1 hr and covers 2592 channels from 119 to 151 MHz. This instrumental setup allows LOTAAS to reach a detection threshold of 1 to 5 mJy for periodic emission. Thus far, the LOTAAS survey has resulted in the discovery of 73 radio pulsars. Among these are two mildly recycled binary millisecond pulsars (P = 13 and 33 ms), as well as the slowest-spinning radio pulsar currently known (P = 23.5 s). The survey has thus far detected 311 known pulsars, with spin periods ranging from 4 ms to 5.0 s and dispersion measures from 3.0 to 217 pc/cc. Known pulsars are detected at flux densities consistent with literature values. We find that the LOTAAS pulsar discoveries have, on average, longer spin periods than the known pulsar population. This may reflect different selection biases between LOTAAS and previous surveys, though it is also possible that slower-spinning pulsars preferentially have steeper radio spectra. LOTAAS is the deepest all-sky pulsar survey using a digital aperture array; we discuss some of the lessons learned that can inform the approach for similar surveys using future radio telescopes such as the Square Kilometre Array., 22 pages, 9 figures, 3 tables. Accepted for publication in A&A
Published: 2019

31. Calibration of the LOFAR low-band antennas using the Galaxy and a model of the signal chain

Author: Olaf Scholten, Heino Falcke, Antonio Bonardi, Tobias Winchen, S. ter Veen, Stijn Buitink, Katie Mulrey, Arthur Corstanje, Pim Schellart, Laura Rossetto, T. N. G. Trinh, Anna Nelles, Satyendra Thoudam, Brian Hare, Jörg R. Hörandel, Pragati Mitra, Jörg P. Rachen, T. Huege, Astronomy and Astrophysics Research Group, Physics, and Elementary Particle Physics
Subjects: Astroparticle physics, Physics, Spectral shape analysis, 010308 nuclear & particles physics, Astrophysics::High Energy Astrophysical Phenomena, Astronomy, Astrophysics::Instrumentation and Methods for Astrophysics, FOS: Physical sciences, Astronomy and Astrophysics, Cosmic ray, LOFAR, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, 7. Clean energy, Signal, Signal chain, Computational physics, 0103 physical sciences, ddc:540, Calibration, Astrophysics - Instrumentation and Methods for Astrophysics, 010303 astronomy & astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), Energy (signal processing), astro-ph.IM
Abstract: The LOw-Frequency ARray (LOFAR) is used to make precise measurements of radio emission from extensive air showers, yielding information about the primary cosmic ray. Interpreting the measured data requires an absolute and frequency-dependent calibration of the LOFAR system response. This is particularly important for spectral analyses, because the shape of the detected signal holds information about the shower development. We revisit the calibration of the LOFAR antennas in the range of 30 - 80 MHz. Using the Galactic emission and a detailed model of the LOFAR signal chain, we find an improved calibration that provides an absolute energy scale and allows for the study of frequency-dependent features in measured signals. With the new calibration, systematic uncertainties of 13% are reached, and comparisons of the spectral shape of calibrated data with simulations show promising agreement., Comment: 23 pages, 10 figures
Published: 2019

32. 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

33. The energy scale of cosmic rays detected with LOFAR

Author: Pragati Mitra, Hershal Pandya, T. N. G. Trinh, Stijn Buitink, Katie Mulrey, Tobias Winchen, Jörg P. Rachen, Heino Falcke, Arthur Corstanje, A. Nelles, Antonio Bonardi, G. K. Krampah, Jörg R. Hörandel, S. ter Veen, Laura Rossetto, T. Huege, Olaf Scholten, and Brian Hare
Subjects: Physics, Range (particle radiation), Physics::Instrumentation and Detectors, Astronomy, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Instrumentation and Methods for Astrophysics, Radiant energy, Cosmic ray, Astrophysics::Cosmology and Extragalactic Astrophysics, LOFAR, Scintillator, Computational physics, Air shower, ddc:530, Antenna (radio), Energy (signal processing)
Abstract: The LOw-Frequency ARray (LOFAR) measures radio emission from extensive air showers. Precise knowledge of the electric field at each antenna in the $30-80$ MHz range is obtained using a newly developed, frequency-dependent calibration built on knowledge of the Galactic emission and a detailed model of the signal chain. The energy fluence for each event is then determined, allowing for the calculation of the radiation energy of the air shower. The radiation energy, corrected for geometrical effects, scales quadratically with the energy contained in the electromagnetic component of the air shower. These measurements, combined with predictions that rely only on first-principle electrodynamics, provide an energy estimate for the primary particle. In this contribution we present the radio-based energy scale of cosmic rays detected with LOFAR, and compare it to particle-based energy measurements made using the scintillator array located at the LOFAR core.
Published: 2019
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34. Status of the Lunar Detection Mode for Cosmic Particles of LOFAR

Author: T. N. G. Trinh, Brian Hare, Satyendra Thoudam, Stijn Buitink, Olaf Scholten, Katharine Mulrey, Anna Nelles, Heino Falcke, Pragati Mitra, Tobias Winchen, Arthur Corstanje, A. Bonardi, S. ter Veen, Laura Rossetto, Pim Schellart, Jörg P. Rachen, Jörg R. Hörandel, Physics, Astronomy and Astrophysics Research Group, Faculty of Sciences and Bioengineering Sciences, Elementary Particle Physics, and Faculty of Economic and Social Sciences and Solvay Business School
Subjects: History, Astrophysics::High Energy Astrophysical Phenomena, Astronomy, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Low frequency, 01 natural sciences, Education, Askaryan effect, Radio telescope, 0103 physical sciences, Instrumentation and Methods for Astrophysics (astro-ph.IM), 010303 astronomy & astrophysics, High Energy Astrophysical Phenomena (astro-ph.HE), Astroparticle physics, Physics, astro-ph.HE, COSMIC cancer database, 010308 nuclear & particles physics, Mode (statistics), Astrophysics::Instrumentation and Methods for Astrophysics, LOFAR, Computer Science Applications, Orders of magnitude (time), Astrophysics::Earth and Planetary Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Instrumentation and Methods for Astrophysics, astro-ph.IM
Abstract: Cosmic particles hitting Earth's moon produce radio emission via the Askaryan effect. If the resulting radio ns-pulse can be detected by radio telescopes, this technique potentially increases the available collective area for ZeV scale particles by several orders of magnitude compared to current experiments. The LOw Frequency ARray (LOFAR) is the largest radio telescope operating in the optimum frequency regime for this technique. In this contribution, we report on the status of the implementation of the lunar detection mode at LOFAR., Comment: Proceedings of the 26th Extended European Cosmic Ray Symposium (ECRS), Barnaul/Belokurikha, 2018
Published: 2019

35. The FRATS project

Author: Arthur Corstanje, C. J. Law, Antonia Rowlinson, Jörg P. Rachen, Jean-Mathias Grießmeier, S. ter Veen, Heino Falcke, Jochen Eislöffel, P. Zarka, T Winchen, Laura Rossetto, J. E. Enriquez, J. W. Broderick, Antonio Bonardi, M. van den Akker, Jörg R. Hörandel, Anna Nelles, Pim Schellart, A. J. van der Horst, J. van Leeuwen, Rene P. Breton, Stephane Corbel, High Energy Astrophys. & Astropart. Phys (API, FNWI), Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), Radboud university [Nijmegen], Jodrell Bank Centre for Astrophysics, University of Manchester [Manchester], Netherlands Institute for Radio Astronomy (ASTRON), 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), Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, 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), PSL Research University (PSL)-PSL Research University (PSL)-Centre National d’Études Spatiales [Paris] (CNES), 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), Radboud University [Nijmegen], Jodrell Bank Centre for Astrophysics (JBCA), 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), 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), 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), and Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)
Subjects: 010504 meteorology & atmospheric sciences, media_common.quotation_subject, Pilot survey, general [Pulsars], Astrophysics, Low frequency, Surveys, 01 natural sciences, surveys, pulsars: general, 0103 physical sciences, instrumentation: interferometers, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, media_common, Physics, [PHYS]Physics [physics], [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], techniques: high angular resolution, Astronomy and Astrophysics, interferometers [Instrumentation], LOFAR, Polarization (waves), high angular resolution [Techniques], Space and Planetary Science, Sky, Radio frequency, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Four-frequency
Abstract: Context. In the previous decade, two new classes of fast radio transients were detected: the Galactic, rotating radio transients (RRATs) and the extragalactic fast radio bursts (FRBs). If the detectable emission of these objects extends to lower radio frequencies, the LOw Frequency ARray (LOFAR) is ideally suited to seek and localize these transients at frequencies of 10–250 MHz. This is due to LOFAR’s sensitivity, diverse beamform capabilities, and transient buffers for the individual elements that allow post-event imaging of events, potentially at arcsecond resolution. Aims. Our aim is to identify and localize pulses at frequencies below 250 MHz and, in the case of nondetections, derive upper limits on the sky and volume rates of FRBs. Methods. A real-time search program for fast radio transients is installed on the LOFAR systems which runs commensally with other observations, and uses the wide incoherent LOFAR beam (11.25 deg2 at 150 MHz). Buffered data from hundreds of dipoles are used to reconstruct the direction and polarization information of the event, and to distinguish between celestial, terrestrial, and instrumental origins. Results. Observations were taken covering either the frequency range 119–151 MHz or in four frequency bands, each of 2 MHz in width, centered at 124, 149, 156, and 185 MHz. A first pilot survey covered a range of dispersion measures (DM) below 120 pc cm−3, focusing on Galactic sources, and resulted in an upper limit on the transient rate at LOFAR frequencies of less than 1500 events per sky per day above a fluency of 1.6 kJy ms for an 8-ms pulse. A second pilot survey covered a range of DMs below 500 pc cm−3, focusing on extragalactic sources to about 1 Gpc, and resulted in an upper limit of 1400 events per sky per day above a fluency of 6.0 kJy ms for an 8-ms pulse. Using a model for the distance-DM relationship, this equates to an upper limit of 134 events per Gpc3 per day.
Published: 2019

36. Influence of atmospheric electric fields on the radio emission from extensive air showers

Author: Heino Falcke, J. E. Enriquez, Pim Schellart, K. D. de Vries, Jörg P. Rachen, Jörg R. Hörandel, Ute Ebert, A. Nelles, Casper Rutjes, T. N. G. Trinh, Arthur Corstanje, A.M. van den Berg, Satyendra Thoudam, S. ter Veen, Laura Rossetto, Stijn Buitink, Christoph Köhn, Olaf Scholten, Elementary Processes in Gas Discharges, Research unit Astroparticle Physics, Physics, Elementary Particle Physics, and Astronomy and Astrophysics Research Group
Subjects: THUNDERSTORMS, Astronomy, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, Radiation, 01 natural sciences, Physics::Geophysics, PHYSICS, Electric field, 0103 physical sciences, 010306 general physics, Physics::Atmospheric and Oceanic Physics, Astroparticle physics, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), 010308 nuclear & particles physics, FLASHES, Astrophysics::Instrumentation and Methods for Astrophysics, LOFAR, Polarization (waves), SIMULATIONS, Computational physics, MODEL, Physics - Atmospheric and Oceanic Physics, 13. Climate action, Atmospheric and Oceanic Physics (physics.ao-ph), Thunderstorm, ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, RADIATION, Astrophysics - High Energy Astrophysical Phenomena
Abstract: The atmospheric electric fields in thunderclouds have been shown to significantly modify the intensity and polarization patterns of the radio footprint of cosmic-ray-induced extensive air showers. Simulations indicated a very nonlinear dependence of the signal strength in the frequency window of 30-80 MHz on the magnitude of the atmospheric electric field. In this work we present an explanation of this dependence based on Monte Carlo simulations, supported by arguments based on electron dynamics in air showers and expressed in terms of a simplified model. We show that by extending the frequency window to lower frequencies, additional sensitivity to the atmospheric electric field is obtained.
Published: 2016

37. LOFAR lightning imaging: mapping lightning with nanosecond precision

Author: Hidde Leijnse, Antonio Bonardi, Jörg P. Rachen, Jörg R. Hörandel, T. N. G. Trinh, Pragati Mitra, Casper Rutjes, Arthur Corstanje, Olaf Scholten, Pim Schellart, Satyendra Thoudam, Tobias Winchen, Ute Ebert, Anna Nelles, S. ter Veen, Laura Rossetto, Heino Falcke, Stijn Buitink, Katie Mulrey, Brian Hare, Elementary Processes in Gas Discharges, Applied Physics and Science Education, and Research unit Astroparticle Physics
Subjects: Atmospheric Science, 010504 meteorology & atmospheric sciences, Astronomy, 01 natural sciences, Radio telescope, Flash (photography), Time of arrival, 0103 physical sciences, Earth and Planetary Sciences (miscellaneous), GeneralLiterature_REFERENCE(e.g.,dictionaries,encyclopedias,glossaries), 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Remote sensing, Spatial structure, LOFAR, Nanosecond, leader propagation, Lightning, Geophysics, time of arrival, Space and Planetary Science, Mapping system, lightning mapping, ARRAY, lightning
Abstract: Lightning mapping technology has proven instrumental in understanding lightning. In this work we present a pipeline that can use lightning observed by the LOw-Frequency ARray (LOFAR) radio telescope to construct a 3-D map of the flash. We show that LOFAR has unparalleled precision, on the order of meters, even for lightning flashes that are over 20km outside the area enclosed by LOFAR antennas (approximate to 3,200km(2)), and can potentially locate over 10,000 sources per lightning flash. We also show that LOFAR is the first lightning mapping system that is sensitive to the spatial structure of the electrical current during individual lightning leader steps.
Published: 2018

38. The Low-Frequency Radio Eclipses of the Black Widow Pulsar J1810+1744

Author: J. W. Broderick, Rene P. Breton, Jason W. T. Hessels, V. I. Kondratiev, Benjamin Stappers, A. O. Clarke, C. G. Bassa, Patrick Weltevrede, Charlotte Sobey, S. ter Veen, J. van Leeuwen, E. J. Polzin, J.-M. Grießmeier, 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), 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)-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), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace ( LPC2E ), Centre National de la Recherche Scientifique ( CNRS ) -Université d'Orléans ( UO ) -Institut national des sciences de l'Univers ( INSU - CNRS ), Unité Scientifique de la Station de Nançay ( USN ), and Institut national des sciences de l'Univers ( INSU - CNRS ) -Observatoire de Paris-Université d'Orléans ( UO ) -Centre National de la Recherche Scientifique ( CNRS )
Subjects: [ PHYS.ASTR ] Physics [physics]/Astrophysics [astro-ph], Astrophysics::High Energy Astrophysical Phenomena, Flux, FOS: Physical sciences, Context (language use), Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Radio telescope, Pulsar, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, pulsars: individual: PSR J1810+1744, 010303 astronomy & astrophysics, astro-ph.HE, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), 010308 nuclear & particles physics, Scattering, scattering, Astrophysics::Instrumentation and Methods for Astrophysics, binaries: eclipsing, Astronomy and Astrophysics, LOFAR, Orbital period, plasmas, Space and Planetary Science, [SDU]Sciences of the Universe [physics], Orbital motion, Astrophysics::Earth and Planetary Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Astrophysics - High Energy Astrophysical Phenomena, stars: mass-loss
Abstract: We have observed and analysed the eclipses of the black widow pulsar J1810+1744 at low radio frequencies. Using LOw-Frequency ARray (LOFAR) and Westerbork Synthesis Radio Telescope observations between 2011--2015 we have measured variations in flux density, dispersion measure and scattering around eclipses. High-time-resolution, simultaneous beamformed and interferometric imaging LOFAR observations show concurrent disappearance of pulsations and total flux from the source during the eclipses, with a $3��$ upper limit of 36 mJy ($, 15 pages, 9 figures
Published: 2018

39. 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

40. LORA: A scintillator array for LOFAR to measure extensive air showers

Author: Maria Krause, Jörg R. Hörandel, A. Horneffer, J. E. Enriquez, Wilfred Frieswijk, A. Nelles, M. van den Akker, Heino Falcke, S. ter Veen, Arthur Corstanje, Pim Schellart, Stijn Buitink, Satyendra Thoudam, Olaf Scholten, Research unit Astroparticle Physics, and KVI - Center for Advanced Radiation Technology
Subjects: Nuclear and High Energy Physics, Physics - Instrumentation and Detectors, Physics::Instrumentation and Detectors, Astronomy, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Cosmic ray, Astrophysics::Cosmology and Extragalactic Astrophysics, LORA, High Energy Physics - Experiment, Radio telescope, High Energy Physics - Experiment (hep-ex), KASCADE, Extensive air showers, Radio detection, Cosmic rays, Instrumentation and Methods for Astrophysics (astro-ph.IM), Instrumentation, Physics::Atmospheric and Oceanic Physics, Astroparticle physics, Physics, Scintillation, Detector, Astrophysics::Instrumentation and Methods for Astrophysics, LOFAR, Instrumentation and Detectors (physics.ins-det), COSMIC-RAYS, RADIO TELESCOPE, Air shower, ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, Scintillation detectors, Astrophysics - Instrumentation and Methods for Astrophysics, EMISSION
Abstract: The measurement of the radio emission from extensive air showers, induced by high-energy cosmic rays is one of the key science projects of the LOFAR radio telescope. The LOfar Radboud air shower Array (LORA) has been installed in the core of LOFAR in the Netherlands. The main purpose of LORA is to measure the properties of air showers and to trigger the read-out of the LOFAR radio antennas to register extensive air showers. The experimental set-up of the array of scintillation detectors and its performance are described., Comment: 10 pages, Accepted for publication in Nuclear Instruments and Methods A
Published: 2014

41. The association of a J-burst with a solar jet

Author: Helmut O. Rucker, Rebecca McFadden, B. Ciardi, J. M. Anderson, H. Munk, J. W. Broderick, O. Wucknitz, H. Paas, E. Juette, W. Reich, Heino Falcke, Matthias Hoeft, Hamish A. S. Reid, Oleg Smirnov, L. Cerrigone, A. G. Polatidis, Philip Best, Emanuela Orrú, Matthias Steinmetz, J. Magdalenic, D. D. Mulcahy, Gottfried Mann, C. Vocks, P. Zarka, V. N. Pandey, Ashish Asgekar, Mark J. Bentum, Gerard H. Kuper, A. Nelles, Annalisa Bonafede, M. Iacobelli, Diana E. Morosan, Dominik J. Schwarz, M. Pandey-Pommier, M. C. Toribio, R. C. Vermeulen, Jochen Eislöffel, Jean-Mathias Griessmeier, M. Tagger, S. ter Veen, A. W. Gunst, S. Duscha, Mario M. Bisi, R. Blaauw, R. J. van Weeren, D. McKay-Bukowski, I. M. Avruch, Peter T. Gallagher, John McKean, Martin Bell, E. de Geus, M. A. Garrett, Richard Fallows, Frank Breitling, Bo Thidé, J. Sluman, Roberto Pizzo, Marcus Brüggen, Satyendra Thoudam, Astronomy, Kapteyn Astronomical Institute, Trinity College Dublin, Netherlands Institute for Radio Astronomy (ASTRON), SUPA School of Physics and Astronomy [Glasgow], University of Glasgow, Leibniz-Institut für Astrophysik Potsdam (AIP), STFC Rutherford Appleton Laboratory (RAL), Science and Technology Facilities Council (STFC), Royal Observatory of Belgium [Brussels] (ROB), Austrian Academy of Sciences (OeAW), Swedish Institute of Space Physics [Uppsala] (IRF), GeoForschungsZentrum - Helmholtz-Zentrum Potsdam (GFZ), Kapteyn Astronomical Institute [Groningen], University of Groningen [Groningen], CSIRO Astronomy and Space Science, Commonwealth Scientific and Industrial Research Organisation [Canberra] (CSIRO), Royal Observatory Edinburgh (ROE), University of Edinburgh, Jacobs University [Bremen], Universität Hamburg (UHH), Max-Planck-Institut für Astrophysik (MPA), Max-Planck-Gesellschaft, 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)-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), Leiden Observatory [Leiden], Universiteit Leiden, Ruhr-Universität Bochum [Bochum], University of Oulu, Radboud University [Nijmegen], 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), Max-Planck-Institut für Radioastronomie (MPIFR), 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, 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), 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), Universiteit Leiden [Leiden], Radboud university [Nijmegen], 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), and Harvard University [Cambridge]-Smithsonian Institution
Subjects: corona [Sun], 010504 meteorology & atmospheric sciences, Astronomy, particle emission [Sun], Astrophysics, 01 natural sciences, ELECTRON-BEAMS, CORONA, Sun: magnetic, Coronal mass ejection, Astrophysics::Solar and Stellar Astrophysics, GeneralLiterature_REFERENCE(e.g.,dictionaries,encyclopedias,glossaries), 010303 astronomy & astrophysics, Sun: magnetic fields, fields, Physics, Jet (fluid), Solar flare, Sun: radio radiation, Astrophysics::Instrumentation and Methods for Astrophysics, FLARE, Astrophysics - Solar and Stellar Astrophysics, magnetic fields [Sun], Physical Sciences, Physics::Space Physics, Astrophysics::Earth and Planetary Astrophysics, FLUX, DYNAMICS-OBSERVATORY SDO, Field line, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astronomy & Astrophysics, ACCELERATION, Computer Science::Digital Libraries, III BURSTS, Sun: particle emission, 0103 physical sciences, Solar and Stellar Astrophysics (astro-ph.SR), 0105 earth and related environmental sciences, Science & Technology, radio radiation [Sun], [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Sun: corona, Northern Hemisphere, Astronomy and Astrophysics, Magnetic reconnection, LOFAR, Physics::History of Physics, X-RAY JETS, 13. Climate action, Space and Planetary Science, Extreme ultraviolet, RADIO-EMISSION
Abstract: Context. The Sun is an active star that produces large-scale energetic events such as solar flares and coronal mass ejections and numerous smaller-scale events such as solar jets. These events are often associated with accelerated particles that can cause emission at radio wavelengths. The reconfiguration of the solar magnetic field in the corona is believed to be the cause of the majority of solar energetic events and accelerated particles. Aims. Here, we investigate a bright J-burst that was associated with a solar jet and the possible emission mechanism causing these two phenomena. Methods. We used data from the Solar Dynamics Observatory (SDO) to observe a solar jet, and radio data from the Low Frequency Array (LOFAR) and the Nan\c{c}ay Radioheliograph (NRH) to observe a J-burst over a broad frequency range (33-173 MHz) on 9 July 2013 at ~11:06 UT. Results. The J-burst showed fundamental and harmonic components and it was associated with a solar jet observed at extreme ultraviolet wavelengths with SDO. The solar jet occurred at a time and location coincident with the radio burst, in the northern hemisphere, and not inside a group of complex active regions in the southern hemisphere. The jet occurred in the negative polarity region of an area of bipolar plage. Newly emerged positive flux in this region appeared to be the trigger of the jet. Conclusions. Magnetic reconnection between the overlying coronal field lines and the newly emerged positive field lines is most likely the cause of the solar jet. Radio imaging provides a clear association between the jet and the J-burst which shows the path of the accelerated electrons., Comment: 11 pages, 8 figures
Published: 2017

42. The circular polarization in radio emission from extensive air showers

Author: Tobias Winchen, Pim Schellart, J. P. Rachen, Jörg R. Hörandel, Arthur Corstanje, A. Nelles, Pragati Mitra, Antonio Bonardi, Heino Falcke, Gia Trinh, Olaf Scholten, Satyendra Thoudam, Brian Hare, S. ter Veen, Laura Rossetto, Stijn Buitink, Katie Mulrey, and Research unit Astroparticle Physics
Subjects: Physics, Frequency band, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Instrumentation and Methods for Astrophysics, LOFAR, Computational physics, Askaryan effect, Azimuth, symbols.namesake, Air shower, Electric field, symbols, Stokes parameters, Circular polarization
Abstract: At LOFAR we measure the radio emission from extensive air showers (EAS) in the frequency band of 30 -- 80~MHz in dual-polarized antennas. Through an accurate antenna calibration we can determine the complete set of four Stokes parameters that uniquely determine the linear and circular polarization of the radio signal for an EAS. The observed dependency of the circular polarization on azimuth angle and distance to the shower axis is explained as due to the interfering contributions from the two different radiation mechanisms, a main contribution due to a geomagnetically-induced transverse current and a secondary component due to the Askaryan effect. The measured data show a quantitative agreement with microscopic CORSIKA/CoREAS calculations. Having a very detailed understanding of radio emission from EAS, opens the possibility to use circular polarization as an investigative tool in the analysis of air shower structure, such as for the determination of atmospheric electric fields.
Published: 2017

43. The effect of the atmospheric refractive index on the radio signal of extensive air showers using Global Data Assimilation System (GDAS)

Author: A. Nelles, J.R. Hörandel, Olaf Scholten, Brian Hare, Satyendra Thoudam, T. N. G. Trinh, Tobias Winchen, Jörg P. Rachen, Pragati Mitra, Antonio Bonardi, Stijn Buitink, Katie Mulrey, Pim Schellart, S. ter Veen, Laura Rossetto, Arthur Corstanje, Heino Falcke, and Research unit Astroparticle Physics
Subjects: Radio telescope, Atmosphere, Data assimilation, Air shower, Frequency band, Environmental science, Cosmic ray, LOFAR, Atmospheric model, Remote sensing
Abstract: In recent years, there has been a rapid advance in the field of radio detection of air showers induced by high-energy cosmic rays. Estimating the depth of shower maximum Xmax with improved accuracy is of great interest for the study of primary particle composition. One of the major systematic uncertainties in the Xmax-measurement arises from variations of the refractive index in the atmosphere. The refractive index varies with temperature, humidity and pressure, and the variations can be on the order of 10% for (n-1) at a given altitude. The effect of a varying refractive index on Xmax-measurements is evaluated using COREAS: a microscopic simulation of the radio emission from the individual particles in the cascade simulated with CORSIKA. We discuss the resulting offsets in Xmax for different frequency regimes, and compare them to a simple physical model. In typical circumstances, the offsets in Xmax range from 4 to 11 g/cm^2 for the 30 to 80 MHz frequency band. Therefore, for precision work it is required to include atmospheric data from the time and place of the air shower into the simulations. The aim is to implement this in the next version of CoREAS/CORSIKA using the Global Data Assimilation System(GDAS), a global atmospheric model based on meteorological measurements and numerical weather predictions. This can then be used to re-evaluate the air shower measurements done with the LOFAR radio telescope.
Published: 2017

44. Thunderstorm electric fields probed by extensive air showers through their polarized radio emission

Author: Olaf Scholten, Anna Nelles, Brian Hare, Tobias Winchen, Pim Schellart, Satyendra Thoudam, Ute Ebert, Casper Rutjes, J. E. Enriquez, S. ter Veen, Laura Rossetto, Pragati Mitra, T. N. G. Trinh, Arthur Corstanje, Jörg P. Rachen, Jörg R. Hörandel, Stijn Buitink, Katie Mulrey, Heino Falcke, Antonio Bonardi, Physics, Astronomy and Astrophysics Research Group, Faculty of Sciences and Bioengineering Sciences, Research unit Astroparticle Physics, and Elementary Processes in Gas Discharges
Subjects: Astronomy, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Atmospheric sciences, 01 natural sciences, symbols.namesake, Electric field, 0103 physical sciences, Stokes parameters, GeneralLiterature_REFERENCE(e.g.,dictionaries,encyclopedias,glossaries), Instrumentation and Methods for Astrophysics (astro-ph.IM), 010303 astronomy & astrophysics, Circular polarization, Physics::Atmospheric and Oceanic Physics, Physics, 010308 nuclear & particles physics, LOFAR, COSMIC-RAYS, Computational physics, Transverse plane, 13. Climate action, symbols, Thunderstorm, RADIATION, ARRAY, Astrophysics - Instrumentation and Methods for Astrophysics
Abstract: We observe a large fraction of circular polarization in radio emission from extensive air showers recorded during thunderstorms, much higher than in the emission from air showers measured during fair-weather circumstances. We show that the circular polarization of the air showers measured during thunderstorms can be explained by the change in the direction of the transverse current as a function of altitude induced by atmospheric electric fields. Thus by using the full set of Stokes parameters for these events, we obtain a good characterization of the electric fields in thunderclouds. We also measure a large horizontal component of the electric fields in the two events that we have analyzed.
Published: 2017

45. The effect of the atmospheric refractive index on the radio signal of extensive air showers

Author: Stijn Buitink, Katie Mulrey, A. Nelles, Tobias Winchen, S. ter Veen, Jörg P. Rachen, Jörg R. Hörandel, Laura Rossetto, Pragati Mitra, Pim Schellart, Antonio Bonardi, Heino Falcke, Arthur Corstanje, Satyendra Thoudam, Gia Trinh, Olaf Scholten, Research unit Astroparticle Physics, Physics, Astronomy and Astrophysics Research Group, Faculty of Sciences and Bioengineering Sciences, and Elementary Particle Physics
Subjects: Astronomy, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Cosmic ray, Atmospheric sciences, 01 natural sciences, 0103 physical sciences, Extensive air showers, Radio emission, Instrumentation and Methods for Astrophysics (astro-ph.IM), 010303 astronomy & astrophysics, Cosmic rays, Zenith, Cherenkov radiation, High Energy Astrophysical Phenomena (astro-ph.HE), Astroparticle physics, Physics, astro-ph.HE, Atmospheric pressure, 010308 nuclear & particles physics, Astrophysics::Instrumentation and Methods for Astrophysics, Humidity, Astronomy and Astrophysics, Atmospheric effects, ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Instrumentation and Methods for Astrophysics, Refractive index, Radio wave, astro-ph.IM
Abstract: For the interpretation of measurements of radio emission from extensive air showers, an important systematic uncertainty arises from natural variations of the atmospheric refractive index $n$. At a given altitude, the refractivity $N=10^6\, (n-1)$ can have relative variations on the order of $10 \%$ depending on temperature, humidity, and air pressure. Typical corrections to be applied to $N$ are about $4\%$. Using CoREAS simulations of radio emission from air showers, we have evaluated the effect of varying $N$ on measurements of the depth of shower maximum $X_{\rm max}$. For an observation band of 30 to 80 MHz, a difference of $4 \%$ in refractivity gives rise to a systematic error in the inferred $X_{\rm max}$ between 3.5 and 11 $\mathrm{g/cm^2}$, for proton showers with zenith angles ranging from 15 to 50 degrees. At higher frequencies, from 120 to 250 MHz, the offset ranges from 10 to 22 $\mathrm{g/cm^2}$. These offsets were found to be proportional to the geometric distance to $X_{\rm max}$. We have compared the results to a simple model based on the Cherenkov angle. For the 120 to 250 MHz band, the model is in qualitative agreement with the simulations. In typical circumstances, we find a slight decrease in $X_{\rm max}$ compared to the default refractivity treatment in CoREAS. While this is within commonly treated systematic uncertainties, accounting for it explicitly improves the accuracy of $X_{\rm max}$ measurements., 13 pages, 5 figures. Accepted for publication in Astroparticle Physics
Published: 2017

46. Search for Cosmic Particles with the Moon and LOFAR

Author: T. N. G. Trinh, Olaf Scholten, S. ter Veen, Jörg P. Rachen, Jörg R. Hörandel, Laura Rossetto, Arthur Corstanje, Anna Nelles, Satyendra Thoudam, Pragati Mitra, Tobias Winchen, J. E. Enriquez, Katharine Mulrey, A. Bonardi, Heino Falcke, Pim Schellart, Stijn Buitink, Research unit Astroparticle Physics, Physics, Astronomy and Astrophysics Research Group, and Faculty of Sciences and Bioengineering Sciences
Subjects: Physics, COSMIC cancer database, 010308 nuclear & particles physics, QC1-999, Astronomy, Astrophysics::High Energy Astrophysical Phenomena, Dark matter, Detector, Astrophysics::Instrumentation and Methods for Astrophysics, FOS: Physical sciences, Cosmic ray, Astrophysics::Cosmology and Extragalactic Astrophysics, LOFAR, Physics and Astronomy(all), 01 natural sciences, Radio telescope, 0103 physical sciences, Particle, Neutrino, Astrophysics - Instrumentation and Methods for Astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), 010303 astronomy & astrophysics, GeneralLiterature_REFERENCE(e.g.,dictionaries,encyclopedias,glossaries)
Abstract: The low flux of the ultra-high energy cosmic rays (UHECR) at the highest energies provides a challenge to answer the long standing question about their origin and nature. A significant increase in the number of detected UHECR is expected to be achieved by employing Earth's moon as detector, and search for short radio pulses that are emitted when a particle interacts in the lunar rock. Observation of these short pulses with current and future radio telescopes also allows to search for the even lower fluxes of neutrinos with energies above $10^{22}$ eV, that are predicted in certain Grand-Unifying-Theories (GUTs), and e.g. models for super-heavy dark matter (SHDM). In this contribution we present the initial design for such a search with the LOFAR radio telescope., Comment: To be published in the Proceedings of the ARENA2016 conference, Groningen, The Netherlands
Published: 2017

47. Realtime processing of LOFAR data for the detection of nano-second pulses from the Moon

Author: Satyendra Thoudam, Tobias Winchen, Pim Schellart, Olaf Scholten, A. Nelles, T. N. G. Trinh, J.R. Hörandel, Stijn Buitink, Katie Mulrey, Antonio Bonardi, Arthur Corstanje, J. E. Enriquez, Heino Falcke, Pragati Mitra, Jörg P. Rachen, S. ter Veen, Laura Rossetto, and Research unit Astroparticle Physics
Subjects: Physics, History, Astronomy, Astrophysics::High Energy Astrophysical Phenomena, Pipeline (computing), Detector, Dark matter, Astrophysics::Instrumentation and Methods for Astrophysics, FOS: Physical sciences, Cosmic ray, 010103 numerical & computational mathematics, LOFAR, 01 natural sciences, Signal, Computer Science Applications, Education, Computational physics, Radio telescope, 0103 physical sciences, 0101 mathematics, Astrophysics - Instrumentation and Methods for Astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), 010303 astronomy & astrophysics, GeneralLiterature_REFERENCE(e.g.,dictionaries,encyclopedias,glossaries), Energy (signal processing)
Abstract: The low flux of the ultra-high energy cosmic rays (UHECR) at the highest energies provides a challenge to answer the long standing question about their origin and nature. Even lower fluxes of neutrinos with energies above $10^{22}$ eV are predicted in certain Grand-Unifying-Theories (GUTs) and e.g.\ models for super-heavy dark matter (SHDM). The significant increase in detector volume required to detect these particles can be achieved by searching for the nano-second radio pulses that are emitted when a particle interacts in Earth's moon with current and future radio telescopes. In this contribution we present the design of an online analysis and trigger pipeline for the detection of nano-second pulses with the LOFAR radio telescope. The most important steps of the processing pipeline are digital focusing of the antennas towards the Moon, correction of the signal for ionospheric dispersion, and synthesis of the time-domain signal from the polyphased-filtered signal in frequency domain. The implementation of the pipeline on a GPU/CPU cluster will be discussed together with the computing performance of the prototype., Proceedings of the 22nd International Conference on Computing in High Energy and Nuclear Physics (CHEP2016), USA
Published: 2017

48. Constraints on the low frequency spectrum of FRB 121102

Author: Heino Falcke, Jörg P. Rachen, S. ter Veen, Laura Spitler, Michael Kramer, and Leon Houben
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE), Physics, education.field_of_study, Spectral index, 010308 nuclear & particles physics, Astronomy, Population, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, LOFAR, Low frequency, 01 natural sciences, Power law, Flattening, Spectral line, Radio telescope, Space and Planetary Science, 0103 physical sciences, ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, Astrophysics - High Energy Astrophysical Phenomena, education, 010303 astronomy & astrophysics
Abstract: While repeating fast radio bursts (FRBs) remain scarce in number, they provide a unique opportunity for follow-up observations that enhance our knowledge of their sources and potentially of the FRB population as a whole. Attaining more burst spectra could lead to a better understanding of the origin of these bright, millisecond-duration radio pulses. We therefore performed $\sim$20 hr of simultaneous observations on FRB 121102 with the Effelsberg 100-m radio telescope and the Low Frequency Array (LOFAR) to constrain the spectral behaviour of bursts from FRB 121102 at 1.4 GHz and 150 MHz. This campaign resulted in the detection of nine new bursts at 1.4 GHz but no simultaneous detections with LOFAR. Assuming that the ratio of the fluence at two frequencies scales as a power law, we placed a lower limit of $��$ > -1.2 $\pm$ 0.4 on the spectral index for the fluence of the instantaneous broad band emission of FRB 121102. For the derivation of this limit, a realistic fluence detection threshold for LOFAR was determined empirically assuming a burst would be scattered as predicted by the NE2001 model. A significant variation was observed in the burst repeat rate R at L-band. During observations in September 2016, nine bursts were detected, giving R = 1.1 $\pm$ 0.4 hr$^{-1}$, while in November no bursts were detected, yielding R < 0.3 hr$^{-1}$ (95% confidence limit). This variation is consistent with earlier seen episodic emission of FRB 121102. In a blind and targeted search, no bursts were found with LOFAR at 150 MHz, resulting in a repeat rate limit of R < 0.16 hr$^{-1}$ (95% confidence limit). Burst repeat rate ratios of FRB 121102 at 3, 2, 1.4, and 0.15 GHz are consistent within the uncertainties with a flattening of its spectrum below 1 GHz., 8 pages, 2 tables, 1 figure
Published: 2019

49. A new parametrization for the radio emission of air showers applied to LOFAR data

Author: Brian Hare, Arthur Corstanje, Antonio Bonardi, Pim Schellart, Pragati Mitra, Tobias Winchen, Jörg R. Hörandel, Heino Falcke, J. P. Rachen, T. N. G. Trinh, I. Plaisier, Satyendra Thoudam, S. ter Veen, Laura Rossetto, Anna Nelles, Stijn Buitink, Katie Mulrey, Olaf Scholten, S. J. De Jong, Astronomy and Astrophysics Research Group, Physics, and Faculty of Sciences and Bioengineering Sciences
Subjects: Physics, QC1-999, Astronomy, Computer Science::Information Retrieval, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Instrumentation and Methods for Astrophysics, Cosmic ray, Astrophysics::Cosmology and Extragalactic Astrophysics, LOFAR, Mass composition, Computational physics, Earth's magnetic field, Primary (astronomy), Energy density, High Energy Physics, Parametrization, Energy (signal processing)
Abstract: The energy and mass composition of cosmic rays influence how the energy density of the radio emission of air showers is distributed on the ground. A precise description of the radio profiles can, therefore, be used to reconstruct the properties of the primary cosmic rays. Here, such a description is presented, using a separate treatment of the two radio-emission mechanisms, the geomagnetic effect and the charge excess effect. The model is parametrized as a function that depends only on the shower parameters, allowing for a precise reconstruction of the properties of the primary cosmic rays. This model is applied to cosmic-ray events measured with LOFAR and it is capable of reconstructing the properties of air showers correctly.
Published: 2019

50. Synchronous X-ray and Radio Mode Switches: A Rapid Global Transformation of the Pulsar Magnetosphere

Author: Y. Tang, Anna M. M. Scaife, Steve Rawlings, Aris Karastergiou, Michael W. Wise, Harvey Butcher, B. Ciardi, S. Duscha, V. N. Pandey, Gianni Bernardi, John McKean, Charlotte Sobey, Emanuela Orrú, Chiara Ferrari, M. Kuniyoshi, H. Munk, Marcus Brüggen, Michael Kramer, Cyril Tasse, J. W. Broderick, E. de Geus, Ashish Asgekar, Jason W. T. Hessels, F. de Gasperin, Matthias Hoeft, George Heald, L. Kuiper, A. P. Schoenmakers, P. Maat, R. H. van de Brink, Sera Markoff, Dipanjan Mitra, Philip Best, G. Wright, Ralph A. M. J. Wijers, J. de Plaa, Heino Falcke, V. I. Kondratiev, Rahul Basu, A. Noutsos, T. Coenen, Benjamin Stappers, Michel Tagger, Frank Breitling, Giulia Macario, Rob Fender, Rene C. Vermeulen, Michael R. Bell, F. Batejat, A. Alexov, Marco Iacobelli, H. Paas, Sarod Yatawatta, Patrick Weltevrede, Tim Hassall, R. J. van Weeren, W. Reich, M. Pilia, Laura Birzan, W. Hermsen, Evan Keane, Aleksandar Shulevski, Mark J. Bentum, M. Serylak, Martin Bell, Annalisa Bonafede, J. van Leeuwen, A. Horneffer, Jochen Eislöffel, Maaijke Mevius, H. J. A. Röttgering, A. G. Polatidis, R. Morganti, I. M. Avruch, S. ter Veen, A. W. Gunst, Olaf Wucknitz, Matthias Steinmetz, M. Pandey-Pommier, K. Zagkouris, J. Sluman, Roberto Pizzo, Jean-Mathias Grießmeier, G. Kuper, Philippe Zarka, Joanna M. Rankin, M. A. Garrett, James Miller-Jones, Wilfred Frieswijk, Hermsen, W., Hessels, J.W.T., Kuiper, L., Van Leeuwen, J., Mitra, D., De Plaa, J., Rankin, J.M., Stappers, B.W., Wright, G.A.E., Basu, R., Alexov, A., Coenen, T., Grießmeier, J.-M., Hassall, T.E., Karastergiou, A., Keane, E., Kondratiev, V.I., Kramer, M., Kuniyoshi, M., Noutsos, A., Serylak, M., Pilia, M., Sobey, C., Weltevrede, P., Zagkouris, K., Asgekar, A., Avruch, I.M., Batejat, F., Bell, M.E., Bell, M.R., Bentum, M.J., Bernardi, G., Best, P., Bîrzan, L., Bonafede, A., Breitling, F., Broderick, J., Brüggen, M., Butcher, H.R., Ciardi, B., Duscha, S., Eislöffel, J., Falcke, H., Fender, R., Ferrari, C., Frieswijk, W., Garrett, M.A., De Gasperin, F., De Geus, E., Gunst, A.W., Heald, G., Hoeft, M., Horneffer, A., Iacobelli, M., Kuper, G., Maat, P., Macario, G., Markoff, S., McKean, J.P., Mevius, M., Miller-Jones, J.C.A., Morganti, R., Munk, H., Orrú, E., Paas, H., Pandey-Pommier, M., Pandey, V.N., Pizzo, R., Polatidis, A.G., Rawlings, S., Reich, W., Röttgering, H., Scaife, A.M.M., Schoenmakers, A., Shulevski, A., Sluman, J., Steinmetz, M., Tagger, M., Tang, Y., Tasse, C., Ter Veen, S., Vermeulen, R., Van De Brink, R.H., Van Weeren, R.J., Wijers, R.A.M.J., Wise, M.W., Wucknitz, O., Yatawatta, S., Zarka, P., SRON Netherlands Institute for Space Research (SRON), University of Amsterdam [Amsterdam] (UvA), National Centre for Radio Astrophysics [Pune] (NCRA), Tata Institute for Fundamental Research (TIFR), University of Vermont [Burlington], Jodrell Bank Centre for Astrophysics, University of Manchester [Manchester], Astronomy Centre, University of Sussex, Space Telescope Science Institute (STSci), Astronomical Institute Anton Pannekoek (AI PANNEKOEK), 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), Oxford Astrophysics, University of Oxford, Centre for Astrophysics and Supercomputing, Swinburne University of Technology [Melbourne], Netherlands Institute for Radio Astronomy (ASTRON), Max-Planck-Institut für Radioastronomie (MPIFR), Onsala Space Observatory (OSO), Chalmers University of Technology [Göteborg], University of Southampton, Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University-Smithsonian Institution, University of Edinburgh, Leiden Observatory [Leiden], Universiteit Leiden, Jacobs University [Bremen], Leibniz-Institut für Astrophysik Potsdam (AIP), Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, 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), Hamburger Sternwarte/Hamburg Observatory, Universität Hamburg (UHH), Medstar Research Institute, Kapteyn Astronomical Institute [Groningen], University of Groningen [Groningen], 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], 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), Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), Argelander-Institut für Astronomie (AlfA), Rheinische Friedrich-Wilhelms-Universität Bonn, ANR-09-JCJC-0001,OPALES(2009), Kapteyn Astronomical Institute, Astronomy, 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], 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), 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), and High Energy Astrophys. & Astropart. Phys (API, FNWI)
Subjects: Electromagnetic field, POLARIZATION, Electromagnetic spectrum, Astrophysics::High Energy Astrophysical Phenomena, Astronomy, FOS: Physical sciences, Magnetosphere, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, EMPIRICAL-THEORY, 01 natural sciences, Binary pulsar, Pulsar, Millisecond pulsar, 0103 physical sciences, 010306 general physics, XMM-NEWTON OBSERVATIONS, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, DRIFTING SUBPULSES, Multidisciplinary, B0943+10, Polarization (waves), GAMMA-RAY, [SDU]Sciences of the Universe [physics], 13. Climate action, ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, RADIATION, EMISSION, Astrophysics - High Energy Astrophysical Phenomena, PHOTON IMAGING CAMERA, POWERED PULSARS, Radio wave
Abstract: Pulsars emit low-frequency radio waves through to high-energy gamma-rays that are generated anywhere from the surface out to the edges of the magnetosphere. Detecting correlated mode changes in the multi-wavelength emission is therefore key to understanding the physical relationship between these emission sites. Through simultaneous observations, we have detected synchronous switching in the radio and X-ray emission properties of PSR B0943+10. When the pulsar is in a sustained radio 'bright' mode, the X-rays show only an un-pulsed, non-thermal component. Conversely, when the pulsar is in a radio 'quiet' mode, the X-ray luminosity more than doubles and a 100%-pulsed thermal component is observed along with the non-thermal component. This indicates rapid, global changes to the conditions in the magnetosphere, which challenge all proposed pulsar emission theories., Paper published in Science including supplementary material
Published: 2013

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