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1. The MeerKAT Pulsar Timing Array: first data release

Author

M T Miles, R M Shannon, M Bailes, D J Reardon, M J Keith, A D Cameron, A Parthasarathy, M Shamohammadi, R Spiewak, W van Straten, S Buchner, F Camilo, M Geyer, A Karastergiou, M Kramer, M Serylak, G Theureau, and V Venkatraman Krishnan

Subjects
High Energy Astrophysical Phenomena (astro-ph.HE), Space and Planetary Science, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Instrumentation and Methods for Astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM)
Abstract

We present the first 2.5 years of data from the MeerKAT Pulsar Timing Array (MPTA), part of MeerTime, a MeerKAT Large Survey Project. The MPTA aims to precisely measure pulse arrival times from an ensemble of 88 pulsars visible from the Southern Hemisphere, with the goal of contributing to the search, detection and study of nanohertz-frequency gravitational waves as part of the International Pulsar Timing Array. This project makes use of the MeerKAT telescope, and operates with a typical observing cadence of two weeks using the L-band receiver that records data from 856-1712 MHz. We provide a comprehensive description of the observing system, software, and pipelines used and developed for the MeerTime project. The data products made available as part of this data release are from the 78 pulsars that had at least $30$ observations between the start of the MeerTime programme in February 2019 and October 2021. These include both sub-banded and band-averaged arrival times, as well as the initial timing ephemerides, noise models, and the frequency-dependent standard templates (portraits) used to derive pulse arrival times. After accounting for detected noise processes in the data, the frequency-averaged residuals of $67$ of the pulsars achieved a root-mean-square residual precision of $< 1 \mu \rm{s}$. We also present a novel recovery of the clock correction waveform solely from pulsar timing residuals, and an exploration into preliminary findings of interest to the international pulsar timing community. The arrival times, standards and full Stokes parameter calibrated pulsar timing archives are publicly available., Comment: 18 pages, 6 figures

Published
2022

2. Four pulsar discoveries in NGC 6624 by TRAPUM using MeerKAT

Author

F Abbate, A Ridolfi, E D Barr, S Buchner, M Burgay, D J Champion, W Chen, P C C Freire, T Gautam, J M Grießmeier, L Künkel, M Kramer, P V Padmanabh, A Possenti, S Ransom, M Serylak, B W Stappers, V Venkatraman Krishnan, J Behrend, R P Breton, L Levin, and Y Men

Subjects
High Energy Astrophysical Phenomena (astro-ph.HE), stars: neutron, Space and Planetary Science, pulsars: general, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, globular clusters: individual: NGC
Abstract

We report 4 new pulsars discovered in the core-collapsed globular cluster (GC) NGC 6624 by the TRAPUM Large Survey Project with the MeerKAT telescope. All of the new pulsars found are isolated. PSR J1823$-$3021I and PSR J1823$-$3021K are millisecond pulsars with period of respectively 4.319 ms and 2.768 ms. PSR J1823$-$3021J is mildly recycled with a period of 20.899 ms, and PSR J1823$-$3022 is a long period pulsar with a period of 2.497 s. The pulsars J1823$-$3021I, J1823$-$3021J, and J1823$-$3021K have position and dispersion measure (DM) compatible with being members of the GC and are therefore associated with NGC 6624. Pulsar J1823$-$3022 is the only pulsar bright enough to be re-detected in archival observations of the cluster. This allowed the determination of a timing solution that spans over two decades. It is not possible at the moment to claim the association of pulsar J1823$-$3022 with the GC given the long period and large offset in position ($\sim 3$ arcminutes) and DM (with a fractional difference of 11 percent compared the average of the pulsars in NGC 6624). The discoveries made use of the beamforming capability of the TRAPUM backend to generate multiple beams in the same field of view which allows sensitive searches to be performed over a few half-light radii from the cluster center and can simultaneously localise the discoveries. The discoveries reflect the properties expected for pulsars in core-collapsed GCs., Accepted for publication on Monthly Notices of the Royal Astronomical Society. 11 pages, 6 figures

Published
2022

3. The Thousand-Pulsar-Array programme on MeerKAT -- VIII. The subpulse modulation of 1198 pulsars

Author

X Song, P Weltevrede, A Szary, G Wright, M J Keith, A Basu, S Johnston, A Karastergiou, R A Main, L S Oswald, A Parthasarathy, B Posselt, M Bailes, S Buchner, B Hugo, and M Serylak

Subjects
High Energy Astrophysical Phenomena (astro-ph.HE), Space and Planetary Science, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics - High Energy Astrophysical Phenomena
Abstract

We report on the subpulse modulation properties of 1198 pulsars using the Thousand-Pulsar-Array programme on MeerKAT. About 35% of the analysed pulsars exhibit drifting subpulses which are more pronounced towards the deathline, consistent with previous studies. We estimate that this common phenomenon is detectable in 60% of the overall pulsar population if high quality data were available for all. This large study reveals the evolution of drifting subpulses across the pulsar population in unprecedented detail. In particular, we find that the modulation period $P_3$ follows a V-shaped evolution with respect to the characteristic age $\tau_c$, such that the smallest $P_3$ values, corresponding to the Nyquist period $P_3>\sim2$, are found at $\tau_c>\sim10^{7.5}$ yr. The V-shaped evolution can be interpreted and reproduced if young pulsars possess aliased fast intrinsic $P_3$, which monotonically increase, ultimately achieving a slow unaliased $P_3$. Enhancement of irregularities in intrinsic subpulse modulation by aliasing in small $\tau_c$ pulsars would explain their observed less well defined $P_3$'s and weaker spectral features. Modelling these results as rotating subbeams, their circulation must slow down as the pulsar evolves. This is the opposite to that expected if circulation is driven by ExB drift. This can be resolved if the observed $P_3$ periodicity is due to a beat between an ExB system and the pulsar period. As a by-product, we identify the correct periods and spin-down rates for 12 pulsars, for which harmonically related values were reported in the literature., Comment: 18 pages, 13 figures in the main part of the paper. This version includes all online materials from the accepted MNRAS article

Published
2023
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4. PSR J1910–5959A: A rare gravitational laboratory for testing white dwarf models

Author

A. Corongiu, V. Venkatraman Krishnan, P. C. C. Freire, M. Kramer, A. Possenti, M. Geyer, A. Ridolfi, F. Abbate, M. Bailes, E. D. Barr, V. Balakrishnan, S. Buchner, D. J. Champion, W. Chen, B. V. Hugo, A. Karastergiou, A. G. Lyne, R. N. Manchester, P. V. Padmanabh, A. Parthasarathy, S. M. Ransom, J. M. Sarkissian, M. Serylak, and W. van Straten

Subjects
High Energy Astrophysical Phenomena (astro-ph.HE), Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, Solar and Stellar Astrophysics (astro-ph.SR)
Abstract

PSRJ1910-5959A (J1910A) is a binary millisecond pulsar in a 0.837 day circular orbit around a helium white dwarf (HeWD) companion. This pulsar is located 6.3 arcmin away from the centre of the globular cluster NGC6752. Given the large offset, the association of the pulsar to NGC6752 has been debated. We have made use of two decades of archival Parkes 64-m "Murriyang" telescope data and recently carried out observations with the MeerKAT telescope. We obtained Pulse times of arrival using standard data reduction techniques and analysed using Bayesian pulsar timing techniques. We analysed the pulsar's total intensity and polarisation profile, to study the interstellar scattering along the line of sight, and the pulsar's geometry by applying the rotating vector model. We obtain precise measurements of several post-Keplerian parameters: the range $r=0.202(6)T_\odot$ and shape s=0.999823(4) of the Shapiro delay, from which we infer the orbital inclination to be $88.9^{+0.15}_{-0.14}\deg$ and the masses of both the pulsar and the companion to be $1.55(7)M_{\odot}$ and $0.202(6)M_{\odot}$ respectively; a secular change in the orbital period $\dot{P}_{\rm b}=-53^{+7.4}_{-6.0}\times 10^{-15}$\,s\,s$^{-1}$ that proves the association to NGGC6752 and a secular change in the projected semi-major axis of the pulsar $\dot{x}= -40.7^{+7.3}_{-8.2}\times10^{-16}$\,s\,s$^{-1}$ that is likely caused by the spin-orbit interaction from a misaligned HeWD spin, at odds with the likely isolated binary evolution of the system. We also discuss some theoretical models for the structure and evolution of WDs in NS-WD binaries by using J1910A's companion as a test bed. J1910A is a rare system for which several parameters of both the pulsar and the HeWD companion can be accurately measured. As such, it is a test bed to discriminate between alternative models for HeWD structure and cooling., Comment: 18 pages, 12 figures. Abstract shortened and rephrased because of arXiv characters limits. Accepted for publication on A&A on January 9th 2023 Updated version after linguistic revision

Published
2023

5. The TRAPUM L-band survey for pulsars in Fermi-LAT gamma-ray sources

Author

C J Clark, R P Breton, E D Barr, M Burgay, T Thongmeearkom, L Nieder, S Buchner, B Stappers, M Kramer, W Becker, M Mayer, A Phosrisom, A Ashok, M C Bezuidenhout, F Calore, I Cognard, P C C Freire, M Geyer, J-M Grießmeier, R Karuppusamy, L Levin, P V Padmanabh, A Possenti, S Ransom, M Serylak, V Venkatraman Krishnan, L Vleeschower, J Behrend, D J Champion, W Chen, D Horn, E F Keane, L Künkel, Y Men, A Ridolfi, V S Dhillon, T R Marsh, M A Papa, and HEP, INSPIRE

Subjects
High Energy Astrophysical Phenomena (astro-ph.HE), stars, Space and Planetary Science, J1526-2744, J1803-6707-gamma rays, general - pulsars, FOS: Physical sciences, Astronomy and Astrophysics, J1036-4353, individual, binaries, [PHYS.ASTR] Physics [physics]/Astrophysics [astro-ph], Astrophysics - High Energy Astrophysical Phenomena
Abstract

More than 100 millisecond pulsars (MSPs) have been discovered in radio observations of gamma-ray sources detected by the Fermi Large Area Telescope (LAT), but hundreds of pulsar-like sources remain unidentified. Here we present the first results from the targeted survey of Fermi-LAT sources being performed by the Transients and Pulsars with MeerKAT (TRAPUM) Large Survey Project. We observed 79 sources identified as possible gamma-ray pulsar candidates by a Random Forest classification of unassociated sources from the 4FGL catalogue. Each source was observed for 10 minutes on two separate epochs using MeerKAT's L-band receiver (856-1712 MHz), with typical pulsed flux density sensitivities of $\sim$100$\,\mu$Jy. Nine new MSPs were discovered, eight of which are in binary systems, including two eclipsing redbacks and one system, PSR J1526$-$2744, that appears to have a white dwarf companion in an unusually compact 5 hr orbit. We obtained phase-connected timing solutions for two of these MSPs, enabling the detection of gamma-ray pulsations in the Fermi-LAT data. A follow-up search for continuous gravitational waves from PSR J1526$-$2744 in Advanced LIGO data using the resulting Fermi-LAT timing ephemeris yielded no detection, but sets an upper limit on the neutron star ellipticity of $2.45\times10^{-8}$. We also detected X-ray emission from the redback PSR J1803$-$6707 in data from the first eROSITA all-sky survey, likely due to emission from an intra-binary shock., Comment: 17 pages, 8 figures, accepted for publication in MNRAS

Published
2022

6. The thousand-pulsar-array programme on MeerKAT VII: polarisation properties of pulsars in the Magellanic Clouds

Author

S Johnston, A Parthasarathy, R A Main, J P Ridley, B S Koribalski, M Bailes, S J Buchner, M Geyer, A Karastergiou, M J Keith, M Kramer, M Serylak, R M Shannon, R Spiewak, and V Venkatraman Krishnan

Subjects
High Energy Astrophysical Phenomena (astro-ph.HE), 010308 nuclear & particles physics, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Instrumentation and Methods for Astrophysics, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics - Astrophysics of Galaxies, 01 natural sciences, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), 0103 physical sciences, Astrophysics - High Energy Astrophysical Phenomena, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics
Abstract

The Magellanic Clouds are the only external galaxies known to host radio pulsars. The dispersion and rotation measures of pulsars in the Clouds can aid in understanding their structure, and studies of the pulsars themselves can point to potential differences between them and their Galactic counterparts. We use the high sensitivity of the MeerKAT telescope to observe 17 pulsars in the Small and Large Magellanic Clouds in addition to five foreground (Galactic) pulsars. We provide polarization profiles for 18 of these pulsars, improved measurements of their dispersion and rotation measures, and derive the mean parallel magnetic field along the lines of sight. The results are broadly in agreement with expectations for the structure and strength of the magnetic field in the Large and Small Magellanic Clouds. The Magellanic Cloud pulsars have profiles which are narrower than expected from the period-width relationship and we show this is due to selection effects in pulsar surveys rather than any intrinsic difference between the population of Galactic and Magellanic objects., Comment: Accepted for publication in MNRAS

Published
2021

7. Gravitational signal propagation in the Double Pulsar studied with the MeerKAT telescope

Author

H. Hu, M. Kramer, D. J. Champion, N. Wex, A. Parthasarathy, T. T. Pennucci, N. K. Porayko, W. van Straten, V. Venkatraman Krishnan, M. Burgay, P. C. C. Freire, R. N. Manchester, A. Possenti, I. H. Stairs, M. Bailes, S. Buchner, A. D. Cameron, F. Camilo, and M. Serylak

Subjects
High Energy Astrophysical Phenomena (astro-ph.HE), Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, FOS: Physical sciences, Astronomy and Astrophysics, General Relativity and Quantum Cosmology (gr-qc), Astrophysics - High Energy Astrophysical Phenomena, Solar and Stellar Astrophysics (astro-ph.SR), General Relativity and Quantum Cosmology
Abstract

The Double Pulsar, PSR J0737-3039A/B, has offered a wealth of gravitational experiments in the strong-field regime, all of which GR has passed with flying colours. In particular, among current gravity experiments that test photon propagation, the Double Pulsar probes the strongest spacetime curvature. Observations with MeerKAT and, in future, the SKA can greatly improve the accuracy of current tests and facilitate tests of NLO contributions in both orbital motion and signal propagation. We present our timing analysis of new observations of PSR J0737-3039A, made using the MeerKAT telescope over the last 3 years. The increased timing precision offered by MeerKAT yields a 2 times better measurement of Shapiro delay parameter s and improved mass measurements compared to previous studies. In addition, our results provide an independent confirmation of the NLO signal propagation effects and already surpass the previous measurement from 16-yr data by a factor of 1.65. These effects include the retardation effect due to the movement of B and the deflection of the signal by the gravitational field of B. We also investigate novel effects which are expected. For instance, we search for potential profile variations near superior conjunctions caused by shifts of the line-of-sight due to latitudinal signal deflection and find insignificant evidence with our current data. With simulations, we find that the latitudinal deflection delay is unlikely to be measured with timing because of its correlation with Shapiro delay. Furthermore, although it is currently not possible to detect the expected lensing correction to the Shapiro delay, our simulations suggest that this effect may be measured with the full SKA. Finally, we provide an improved analytical description for the signal propagation in the Double Pulsar system that meets the timing precision expected from future instruments such as the full SKA., 13 pages, 13 figures, accepted for publication in A&A

Published
2022

8. The thousand-pulsar-array programme on MeerKAT IV: Polarization properties of young, energetic pulsars

Author

Daniel J. Reardon, Aris Karastergiou, Fernando Camilo, M. Serylak, Michael Kramer, Ryan Shannon, Renée Spiewak, Michael Keith, W. van Straten, Aditya Parthasarathy, V. Venkatraman Krishnan, Andrew Jameson, B. Hugo, Matthew Bailes, M. Geyer, Simon Johnston, Ewan Barr, S. Buchner, and Patrick Weltevrede

Subjects
High Energy Astrophysical Phenomena (astro-ph.HE), Physics, 010308 nuclear & particles physics, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Instrumentation and Methods for Astrophysics, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, Polarization (waves), 01 natural sciences, Astrophysics - Solar and Stellar Astrophysics, Pulsar, Space and Planetary Science, 0103 physical sciences, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Instrumentation and Methods for Astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR)
Abstract

We present observations of 35 high spin-down energy radio pulsars using the MeerKAT telescope. Polarisation profiles and associated parameters are also presented. We derive the geometry for a selection of pulsars which show interpulse emission. We point out that, in several cases, these radio pulsars should also be seen in $\gamma$-rays but that improved radio timing is required to aid the high-energy detection. We discuss the relationship between the width of the radio profile and its high-energy detectability. Finally, we reflect on the correlation between the spin-down energy and the radio polarisation fraction and the implications this may have for $\gamma$-ray emission., Comment: 11 pages, 4 figures, accepted for publication by the MNRAS

Published
2021

9. The Thousand-Pulsar-Array programme on MeerKAT – V. Scattering analysis of single-component pulsars

Author

M. Serylak, Ryan Shannon, Bettina Posselt, Aris Karastergiou, Simon Johnston, S. Buchner, Matthew Bailes, W. van Straten, R. Spiewak, Michael Kramer, Daniel J. Reardon, Michael Keith, L. S. Oswald, M. Geyer, Aditya Parthasarathy, and V. Venkatraman Krishnan

Subjects
High Energy Astrophysical Phenomena (astro-ph.HE), Physics, Spectral index, Line-of-sight, 010308 nuclear & particles physics, Scattering, Gaussian, Isotropy, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, 01 natural sciences, Standard deviation, law.invention, Telescope, symbols.namesake, Pulsar, Space and Planetary Science, law, 0103 physical sciences, symbols, Astrophysics - High Energy Astrophysical Phenomena, 010303 astronomy & astrophysics
Abstract

We have measured the scattering timescale, $\tau$, and the scattering spectral index, $\alpha$, for 84 single-component pulsars. Observations were carried out with the MeerKAT telescope as part of the Thousand-Pulsar-Array programme in the MeerTime project at frequencies between 0.895 and 1.670 GHz. Our results give a distribution of values for $\alpha$ (defined in terms of $\tau$ and frequency $\nu$ as $\tau\propto\nu^{-\alpha}$) for which, upon fitting a Gaussian, we obtain a mean and standard deviation of $\langle\alpha\rangle = 4.0 \pm 0.6$. This is due to our identification of possible causes of inaccurate measurement of $\tau$, which, if not filtered out of modelling results, tend to lead to underestimation of $\alpha$. The pulsars in our sample have large dispersion measures and are therefore likely to be distant. We find that a model using an isotropic scatter broadening function is consistent with the data, likely due to the averaging effect of multiple scattering screens along the line of sight. Our sample of scattering parameters provides a strong data set upon which we can build to test more complex and time-dependent scattering phenomena, such as extreme scattering events., Comment: Accepted for publication in MNRAS. 14 pages, 14 figures, 2 tables

Published
2021

10. First discoveries and localisations of Fast Radio Bursts with MeerTRAP: a real-time, commensal MeerKAT survey

Author

K M Rajwade, M C Bezuidenhout, M Caleb, L N Driessen, F Jankowski, M Malenta, V Morello, S Sanidas, B W Stappers, M P Surnis, E D Barr, W Chen, M Kramer, J Wu, S Buchner, M Serylak, F Combes, W Fong, N Gupta, P Jagannathan, C D Kilpatrick, J-K Krogager, P Noterdaeme, C Núnẽz, J Xavier Prochaska, R Srianand, and N Tejos

Subjects
High Energy Astrophysical Phenomena (astro-ph.HE), Space and Planetary Science, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics - High Energy Astrophysical Phenomena
Abstract

We report on the discovery and localization of fast radio bursts (FRBs) from the MeerTRAP project, a commensal fast radio transient-detection programme at MeerKAT in South Africa. Our hybrid approach combines a coherent search with an average field-of-view of 0.4 $\rm deg^{2}$ with an incoherent search utilizing a field-of-view of $\sim$1.27 $\rm deg^{2}$ (both at 1284~MHz). Here, we present results on the first three FRBs: FRB 20200413A (DM=1990.05 pc cm$^{-3}$), FRB 20200915A (DM=740.65 pc cm$^{-3}$), and FRB 20201123A (DM=433.55 pc cm$^{-3}$). FRB 20200413A was discovered only in the incoherent beam. FRB 20200915A (also discovered only in the incoherent beam) shows speckled emission in the dynamic spectrum which cannot be explained by interstellar scintillation in our Galaxy or plasma lensing, and might be intrinsic to the source. FRB 20201123A shows a faint post-cursor burst about 200 ms after the main burst and warrants further follow-up to confirm whether it is a repeating FRB. FRB 20201123A also exhibits significant temporal broadening consistent with scattering by a turbulent medium. The broadening exceeds that predicted for medium along the sightline through our Galaxy. We associate this scattering with the turbulent medium in the environment of the FRB in the host galaxy. Within the approximately $1'$ localization region of FRB 20201123A, we identify one luminous galaxy ($r \approx 15.67$; J173438.35$-$504550.4) that dominates the posterior probability for a host association. The galaxy's measured properties are consistent with other FRB hosts with secure associations., 14 pages, 9 figures, 3 tables, accepted for publication in MNRAS

Published
2022

11. The eccentric millisecond pulsar, PSR J0955$-$6150 I: Pulse profile analysis, mass measurements and constraints on binary evolution

Author

M. Serylak, V. Venkatraman Krishnan, P. C. C. Freire, T. M. Tauris, M. Kramer, M. Geyer, A. Parthasarathy, M. Bailes, M. C. i Bernadich, S. Buchner, M. Burgay, F. Camilo, A. Karastergiou, M. E. Lower, A. Possenti, D. J. Reardon, R. M. Shannon, R. Spiewak, I. H. Stairs, and W. van Straten

Subjects
High Energy Astrophysical Phenomena (astro-ph.HE), general [Binaries], Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, FOS: Physical sciences, Astronomy and Astrophysics, neutron [Stars], Astrophysics - High Energy Astrophysical Phenomena, individual: PSR J0955- 6150 [Pulsars], Solar and Stellar Astrophysics (astro-ph.SR)
Abstract

PSR J0955$-$6150 is a member of a class of eccentric MSP+He WD systems (eMSPs), whose binary evolution is poorly understood and believed to be different to that of traditional MSP+He WD systems. Measuring the masses of the stars in this system is important for testing hypotheses for the formation of eMSPs. We have carried out observations of this pulsar with the Parkes and MeerKAT radio telescopes. Our observations reveal a strong frequency evolution of this pulsar's intensity, with a spectral index ($\alpha$) of $-3.13(2)$. The sensitivity of MeerKAT has resulted in a $>10$-fold improvement in the timing precision compared to older Parkes observations. Combined with the 8-year timing baseline, it has allowed precise measurements of a proper motion and three orbital "post-Keplerian" parameters: the rate of advance of periastron, $\dot{\omega} = 0.00152(1) \, {\rm deg} \, yr^{-1}$ and the orthometric Shapiro delay parameters, $h_3 = 0.89(7) \, \mu$s and $\varsigma = 0.88(2)$. Assuming general relativity, we obtain $M_{p} = 1.71(2) \, M_{\odot}$ for the mass of the pulsar and $M_{c} = 0.254(2) \, M_{\odot}$ for the mass of the companion; the orbital inclination is 83.2(4) degrees. We find that the spin axis has a misalignment relative to the orbital angular momentum of $> 4.8$ degrees at 99% CI. While the value of $M_{\rm p}$ falls within the wide range observed in eMSPs, $M_{\rm c}$ is significantly smaller than expected, allowing several formation hypotheses being ruled out. $M_{\rm c}$ is also significantly different from the expected value for an ideal low mass X-ray binary evolution scenario. The putative misalignment between the spin axis of the pulsar and the orbital angular momentum suggests that the unknown process that created the orbital eccentricity of the binary was also capable of changing its orbital orientation, an important evidence for understanding the origin of eMSPs., Comment: 20 pages, 9 figures, 5 tables, accepted for publication by the A&A

Published
2022

12. The 1.28 GHz MeerKAT Galactic Center Mosaic

Author

I. Heywood, I. Rammala, F. Camilo, W. D. Cotton, F. Yusef-Zadeh, T. D. Abbott, R. M. Adam, G. Adams, M. A. Aldera, K. M. B. Asad, E. F. Bauermeister, T. G. H. Bennett, H. L. Bester, W. A. Bode, D. H. Botha, A. G. Botha, L. R. S. Brederode, S. Buchner, J. P. Burger, T. Cheetham, D. I. L. de Villiers, M. A. Dikgale-Mahlakoana, L. J. du Toit, S. W. P. Esterhuyse, B. L. Fanaroff, S. February, D. J. Fourie, B. S. Frank, R. R. G. Gamatham, M. Geyer, S. Goedhart, M. Gouws, S. C. Gumede, M. J. Hlakola, A. Hokwana, S. W. Hoosen, J. M. G. Horrell, B. Hugo, A. I. Isaacson, G. I. G. Józsa, J. L. Jonas, A. F. Joubert, R. P. M. Julie, F. B. Kapp, J. S. Kenyon, P. P. A. Kotzé, N. Kriek, H. Kriel, V. K. Krishnan, R. Lehmensiek, D. Liebenberg, R. T. Lord, B. M. Lunsky, K. Madisa, L. G. Magnus, O. Mahgoub, A. Makhaba, S. Makhathini, J. A. Malan, J. R. Manley, S. J. Marais, A. Martens, T. Mauch, B. C. Merry, R. P. Millenaar, N. Mnyandu, O. J. Mokone, T. E. Monama, M. C. Mphego, W. S. New, B. Ngcebetsha, K. J. Ngoasheng, M. T. Ockards, N. Oozeer, A. J. Otto, S. S. Passmoor, A. A. Patel, A. Peens-Hough, S. J. Perkins, A. J. T. Ramaila, N. M. R. Ramanujam, Z. R. Ramudzuli, S. M. Ratcliffe, A. Robyntjies, S. Salie, N. Sambu, C. T. G. Schollar, L. C. Schwardt, R. L. Schwartz, M. Serylak, R. Siebrits, S. K. Sirothia, M. Slabber, O. M. Smirnov, L. Sofeya, B. Taljaard, C. Tasse, A. J. Tiplady, O. Toruvanda, S. N. Twum, T. J. van Balla, A. van der Byl, C. van der Merwe, V. Van Tonder, R. Van Wyk, A. J. Venter, M. Venter, B. H. Wallace, M. G. Welz, L. P. Williams, and B. Xaia

Subjects
Space and Planetary Science, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics of Galaxies (astro-ph.GA), FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics - Astrophysics of Galaxies, Astrophysics::Galaxy Astrophysics
Abstract

The inner $\sim$200 pc region of the Galaxy contains a 4 million M$_{\odot}$ supermassive black hole (SMBH), significant quantities of molecular gas, and star formation and cosmic ray energy densities that are roughly two orders of magnitude higher than the corresponding levels in the Galactic disk. At a distance of only 8.2 kpc, the region presents astronomers with a unique opportunity to study a diverse range of energetic astrophysical phenomena, from stellar objects in extreme environments, to the SMBH and star-formation driven feedback processes that are known to influence the evolution of galaxies as a whole. We present a new survey of the Galactic center conducted with the South African MeerKAT radio telescope. Radio imaging offers a view that is unaffected by the large quantities of dust that obscure the region at other wavelengths, and a scene of striking complexity is revealed. We produce total intensity and spectral index mosaics of the region from 20 pointings (144 hours on-target in total), covering 6.5 square degrees with an angular resolution of 4$"$,at a central frequency of 1.28 GHz. Many new features are revealed for the first time due to a combination of MeerKAT's high sensitivity, exceptional $u,v$-plane coverage, and geographical vantage point. We highlight some initial survey results, including new supernova remnant candidates, many new non-thermal filament complexes, and enhanced views of the Radio Arc Bubble, Sgr A and Sgr B regions. This project is a SARAO public legacy survey, and the image products are made available with this article., Comment: 29 pages, 15 figures, 3 tables, accepted for publication in the The Astrophysical Journal. Replacement arXiv version with higher quality figures

Published
2022
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13. The MeerTime Pulsar Timing Array -- A Census of Emission Properties and Timing Potential

Author

R. Spiewak, M. Bailes, M. T. Miles, A. Parthasarathy, D. J. Reardon, M. Shamohammadi, R. M. Shannon, N. D. R. Bhat, S. Buchner, A. D. Cameron, F. Camilo, M. Geyer, S. Johnston, A. Karastergiou, M. Keith, M. Kramer, M. Serylak, W. van Straten, G. Theureau, and V. Venkatraman Krishnan

Subjects
High Energy Astrophysical Phenomena (astro-ph.HE), Space and Planetary Science, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics - High Energy Astrophysical Phenomena
Abstract

MeerTime is a five-year Large Survey Project to time pulsars with MeerKAT, the 64-dish South African precursor to the Square Kilometre Array. The science goals for the programme include timing millisecond pulsars (MSPs) to high precision (< 1 $\mu$s) to study the Galactic MSP population and to contribute to global efforts to detect nanohertz gravitational waves with the International Pulsar Timing Array (IPTA). In order to plan for the remainder of the programme and to use the allocated time most efficiently, we have conducted an initial census with the MeerKAT "L-band" receiver of 189 MSPs visible to MeerKAT and here present their dispersion measures, polarization profiles, polarization fractions, rotation measures, flux density measurements, spectral indices, and timing potential. As all of these observations are taken with the same instrument (which uses coherent dedispersion, interferometric polarization calibration techniques, and a uniform flux scale), they present an excellent resource for population studies. We used wideband pulse portraits as timing standards for each MSP and demonstrated that the MeerTime Pulsar Timing Array (MPTA) can already contribute significantly to the IPTA as it currently achieves better than 1 $\mu$s timing accuracy on 89 MSPs (observed with fortnightly cadence). By the conclusion of the initial five-year MeerTime programme in July 2024, the MPTA will be extremely significant in global efforts to detect the gravitational wave background with a contribution to the detection statistic comparable to other long-standing timing programmes., Comment: Accepted to PASA. 27 figures. Data to be made available under the DOI 10.5281/zenodo.5347875 at the time of publication

Published
2022
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14. The LOFAR Tied-Array All-Sky Survey: Timing of 35 radio pulsars and an overview of the properties of the LOFAR pulsar discoveries

Author

E. van der Wateren, C. G. Bassa, S. Cooper, J.-M. Grießmeier, B. W. Stappers, J. W. T. Hessels, V. I. Kondratiev, D. Michilli, C. M. Tan, C. Tiburzi, P. Weltevrede, A.-S. Bak Nielsen, T. D. Carozzi, B. Ciardi, I. Cognard, R.-J. Dettmar, A. Karastergiou, M. Kramer, J. Künsemöller, S. Osłowski, M. Serylak, C. Vocks, and O. Wucknitz

Subjects
High Energy Astrophysical Phenomena (astro-ph.HE), general, Space and Planetary Science, Astronomy, pulsars, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics - High Energy Astrophysical Phenomena
Abstract

The LOFAR Tied-Array All-Sky Survey (LOTAAS) is the most sensitive untargeted radio pulsar survey performed at low radio frequencies (119--151\,MHz) to date and has discovered 76 new radio pulsars, among which the 23.5-s pulsar J0250+5854, up until recently the slowest-spinning radio pulsar known. Here, we report on the timing solutions of 35 pulsars discovered by LOTAAS, which include a nulling pulsar and a mildly recycled pulsar, and thereby complete the full timing analysis of the LOTAAS pulsar discoveries. We give an overview of the findings from the full LOTAAS sample of 76 pulsars, discussing their pulse profiles, radio spectra and timing parameters. We found that the pulse profiles of some of the pulsars show profile variations in time or frequency and while some pulsars show signs of scattering, a large majority display no pulse broadening. The LOTAAS discoveries have on average steeper radio spectra and have longer spin periods ($1.4\times$) as well as lower spin-down rates ($3.1\times$) compared to the known pulsar population. We discuss the cause of these differences, and attribute them to a combination of selection effects of the LOTAAS survey as well as previous pulsar surveys, though can not rule out that older pulsars tend to have steeper radio spectra., Comment: Accepted to Astronomy & Astrophysics

Published
2023

15. Simultaneous X-ray and radio observations of the transitional millisecond pulsar candidate CXOU J110926.4-650224: The discovery of a variable radio counterpart

Author

Simone Migliari, Thomas D. Russell, Sergio Campana, D. de Martino, R. van Rooyen, David A. H. Buckley, F. Coti Zelati, Carlo Ferrigno, J. Li, B. Hugo, Nanda Rea, Diego F. Torres, Alessandro Papitto, I. M. Monageng, Ben Stappers, N. Titus, Enrico Bozzo, M. Serylak, and ESP

Subjects
Accretion, Radio continuum: stars, Astrophysics::High Energy Astrophysical Phenomena, general [Pulsars], FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Luminosity, law.invention, Telescope, X-rays: binaries, Millisecond pulsar, law, 0103 physical sciences, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), 010308 nuclear & particles physics, jets and outflows [ISM], X-ray, Astronomy and Astrophysics, neutron [Stars], Stars: neutron, Pulsars: general, ISM: jets and outflows, 13. Climate action, Space and Planetary Science, Accretion disks, Satellite, stars [Radio continuum], binaries [X-rays], Radio frequency, Astrophysics - High Energy Astrophysical Phenomena, Flare
Abstract

We present the results of simultaneous observations of the transitional millisecond pulsar (tMSP) candidate CXOU J110926.4-650224 with the XMM-Newton satellite and the MeerKAT telescope. The source was found at an average X-ray luminosity of $L_{\rm X}\simeq7\times10^{33}$ erg s$^{-1}$ over the 0.3-10 keV band (assuming a distance of 4 kpc) and displayed a peculiar variability pattern in the X-ray emission, switching between high, low and flaring modes on timescales of tens of seconds. A radio counterpart was detected at a significance of 7.9$\sigma$ with an average flux density of $\simeq$33$\mu$Jy at 1.28 GHz. It showed variability over the course of hours and emitted a $\simeq$10-min long flare just a few minutes after a brief sequence of multiple X-ray flares. No clear evidence for a significant correlated or anticorrelated variability pattern was found between the X-ray and radio emissions over timescales of tens of minutes and longer. CXOU J110926.4-650224 was undetected at higher radio frequencies in subsequent observations performed with the Australia Telescope Compact Array, when the source was still in the same X-ray sub-luminous state observed before, down to a flux density upper limit of 15$\mu$Jy at 7.25 GHz (at 3$\sigma$). We compare the radio emission properties of CXOU J110926.4-650224 with those observed in known and candidate tMSPs and discuss physical scenarios that may account for its persistent and flaring radio emissions., Comment: 10 pages, 4 figures. Accepted for publication on A&A

Published
2021

16. The Thousand-Pulsar-Array programme on MeerKAT – VI. Pulse widths of a large and diverse sample of radio pulsars

Author

Simon Johnston, Ryan Shannon, M. Serylak, Aris Karastergiou, R. Spiewak, L. S. Oswald, V. Venkatraman Krishnan, Ewan Barr, X. Song, M. Geyer, S. Buchner, Patrick Weltevrede, Aditya Parthasarathy, Bettina Posselt, Daniel J. Reardon, Michael Kramer, and Michael Keith

Subjects
High Energy Astrophysical Phenomena (astro-ph.HE), Rotation period, Physics, education.field_of_study, 010504 meteorology & atmospheric sciences, 010308 nuclear & particles physics, Population, Phase (waves), FOS: Physical sciences, Astronomy and Astrophysics, Density estimation, Astrophysics, Rotation, 01 natural sciences, Power law, Spectral line, Astrophysics - Solar and Stellar Astrophysics, Pulsar, Space and Planetary Science, 0103 physical sciences, Astrophysics - High Energy Astrophysical Phenomena, education, Solar and Stellar Astrophysics (astro-ph.SR), 0105 earth and related environmental sciences
Abstract

We present pulse width measurements for a sample of radio pulsars observed with the MeerKAT telescope as part of the Thousand-Pulsar-Array (TPA) programme in the MeerTime project. For a centre frequency of 1284 MHz, we obtain 762 $W_{10}$ measurements across the total bandwidth of 775 MHz, where $W_{10}$ is the width at the 10% level of the pulse peak. We also measure about 400 $W_{10}$ values in each of the four or eight frequency sub-bands. Assuming, the width is a function of the rotation period P, this relationship can be described with a power law with power law index $\mu=-0.29\pm 0.03$. However, using orthogonal distance regression, we determine a steeper power law with $\mu=-0.63\pm 0.06$. A density plot of the period-width data reveals such a fit to align well with the contours of highest density. Building on a previous population synthesis model, we obtain population-based estimates of the obliquity of the magnetic axis with respect to the rotation axis for our pulsars. Investigating the width changes over frequency, we unambiguously identify a group of pulsars that have width broadening at higher frequencies. The measured width changes show a monotonic behaviour with frequency for the whole TPA pulsar population, whether the pulses are becoming narrower or broader with increasing frequency. We exclude a sensitivity bias, scattering and noticeable differences in the pulse component numbers as explanations for these width changes, and attempt an explanation using a qualitative model of five contributing Gaussian pulse components with flux density spectra that depend on their rotational phase., Comment: Accepted for publication in MNRAS. 20 pages, 19 figures, 7 tables

Published
2021

17. Follow-up of 27 radio-quiet gamma-ray pulsars at 110-190 MHz using the international LOFAR station FR606

Author

Gilles Theureau, Matthew Kerr, Tyrel J. Johnson, Jean-Mathias Grießmeier, David A. Smith, Ismaël Cognard, M. Serylak, L. Bondonneau, 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), Centre d'Etudes Nucléaires de Bordeaux Gradignan (CENBG), Université Sciences et Technologies - Bordeaux 1-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Univers et Théories (LUTH (UMR_8102)), 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), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), 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
Astrophysics::High Energy Astrophysical Phenomena, Population, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Low frequency, 01 natural sciences, law.invention, Telescope, Pulsar, law, 0103 physical sciences, education, 010303 astronomy & astrophysics, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, education.field_of_study, 010308 nuclear & particles physics, Computer Science::Information Retrieval, Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy and Astrophysics, LOFAR, Space and Planetary Science, [SDU]Sciences of the Universe [physics], Radio frequency, Antenna (radio), [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Astrophysics - High Energy Astrophysical Phenomena, Fermi Gamma-ray Space Telescope
Abstract

The Fermi Large Area Telescope has detected over 260 gamma-ray pulsars. About one quarter of these are labeled as radio-quiet. In the population of nonrecycled gamma-ray pulsars, the fraction of radio-quiet pulsars is higher, about one half. Most radio observations of gamma-ray pulsars have been performed at frequencies between 300 MHz and 2 GHz. However, pulsar radio fluxes increase rapidly with decreasing frequency, and their radio beams often broaden at low frequencies. As a consequence, some of these pulsars might be detectable at low radio frequencies even when no radio flux is detected above 300 MHz. Our aim is to test this hypothesis with low-frequency radio observations. We have observed 27 Fermi-discovered gamma-ray pulsars with the international LOw Frequency ARray (LOFAR) station FR606 in single-station mode. We used the LOFAR high band antenna (HBA) band (110-190 MHz). On average, we use 9 h of observation per target after the removal of affected datasets, resulting in a sensitivity for pulse-averaged flux on the order of 1-10 mJy. We do not detect radio pulsations from any of the 27 sources, and we establish stringent upper limits on their low-frequency radio fluxes. These nondetections are compatible with the upper limits derived from radio observations at other frequencies. We also determine the pulsars' geometry from the gamma-ray profiles to see for which pulsars the low-frequency radio beam is expected to cross Earth. This set of observations provides the most constraining upper limits on the flux density at 150 MHz for 27 radio-quiet gamma-ray pulsars. In spite of the beam-widening expected at low radio frequencies, most of our nondetections can be explained by an unfavorable viewing geometry; for the remaining observations, especially those of pulsars detected at higher frequencies, the nondetection is compatible with insufficient sensitivity., 17 pages, 3 figures, 1 appendix. Accepted by A&A

Published
2021

18. TRAPUM discovery of 13 new pulsars in NGC 1851 using MeerKAT

Author

A. Ridolfi, P. C. C. Freire, T. Gautam, S. M. Ransom, E. D. Barr, S. Buchner, M. Burgay, F. Abbate, V. Venkatraman Krishnan, L. Vleeschower, A. Possenti, B. W. Stappers, M. Kramer, W. Chen, P. V. Padmanabh, D. J. Champion, M. Bailes, L. Levin, E. F. Keane, R. P. Breton, M. Bezuidenhout, J.-M. Grießmeier, L. Künkel, Y. Men, F. Camilo, M. Geyer, B. V. Hugo, A. Jameson, A. Parthasarathy, and M. Serylak

Subjects
Space and Planetary Science, Astronomy and Astrophysics
Abstract

We report the discovery of 13 new pulsars in the globular cluster NGC 1851 by the TRAPUM Large Survey Project using the MeerKAT radio telescope. The discoveries consist of six isolated millisecond pulsars (MSPs) and seven binary pulsars, of which six are MSPs and one is mildly recycled. For all the pulsars, we present the basic kinematic, astrometric, and orbital parameters, where applicable, as well as their polarimetric properties, when these are measurable. Two of the binary MSPs (PSR J0514−4002D and PSR J0514−4002E) are in wide and extremely eccentric (e > 0.7) orbits with a heavy white dwarf and a neutron star as their companion, respectively. With these discoveries, NGC 1851 is now tied with M28 as the cluster with the third largest number of known pulsars (14). Its pulsar population shows remarkable similarities with that of M28, Terzan 5, and other clusters with comparable structural parameters. The newly found pulsars are all located in the innermost regions of NGC 1851 and will likely enable, among other things, detailed studies of the cluster structure and dynamics.

Published
2022

19. Testing the accuracy of the ionospheric Faraday rotation corrections through LOFAR observations of bright northern pulsars

Author

M. Serylak, Michael Kramer, Marcus Brüggen, A. Horneffer, James M. Anderson, A. Noutsos, J. Künsemöller, Olaf Wucknitz, Dominik J. Schwarz, Caterina Tiburzi, Dominic Schnitzeler, N. K. Porayko, Stefan Oslowski, Joris P. W. Verbiest, Matthias Hoeft, J.-M. Grießmeier, Max-Planck-Institut für Radioastronomie (MPIFR), Universität Bielefeld, Swinburne University of Technology [Melbourne], University of Hamburg, Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National d’Études Spatiales [Paris] (CNES), Unité Scientifique de la Station de Nançay (USN), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), and Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)

Subjects
Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics, 01 natural sciences, Physics::Geophysics, stars: neutron, symbols.namesake, Pulsar, pulsars: general, 0103 physical sciences, Faraday effect, Instrumentation and Methods for Astrophysics (astro-ph.IM), 010303 astronomy & astrophysics, [PHYS]Physics [physics], Physics, polarization, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], 010308 nuclear & particles physics, Astronomy and Astrophysics, LOFAR, Polarization (waves), Magnetic field, Earth's magnetic field, Space and Planetary Science, Physics::Space Physics, symbols, Ionosphere, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Astrophysics - Instrumentation and Methods for Astrophysics, Interplanetary spaceflight, atmospheric effects
Abstract

Faraday rotation of polarized emission from pulsars measured at radio frequencies provides a powerful tool to investigate the interstellar and interplanetary magnetic fields. However, besides being sensitive to the astrophysical media, pulsar observations in radio are affected by the highly time-variable ionosphere. In this article, the amount of ionospheric Faraday rotation has been computed by assuming a thin layer model. For this aim, ionospheric maps of the free electron density (based on Global Positioning System data) and semi-empirical geomagnetic models are needed. Through the data of five highly polarized pulsars observed with the individual German LOw-Frequency ARray stations, we investigate the performances of the ionospheric modelling. In addition, we estimate the parameters of the systematics and the correlated noise generated by the residual unmodelled ionospheric effects, and show the comparison of the different free-electron density maps. For the best ionospheric maps, we have found that the rotation measure corrections on one-year timescales after subtraction of diurnal periodicity are accurate to $\sim$ 0.06--0.07 rad m$^{-2}$., 18 pages, 13 figures, 4 tables

Published
2018

20. The Thousand-Pulsar-Array programme on MeerKAT III: Giant pulse characteristics of PSR J0540$-$6919

Author

R. A. Main, F. Abbate, M. Serylak, Simon Johnston, S. Buchner, Matthew Bailes, Aris Karastergiou, J Chilufya, W. van Straten, M. Geyer, and M. Shamohammadi

Subjects
Physics, High Energy Astrophysical Phenomena (astro-ph.HE), Scintillation, 010308 nuclear & particles physics, Crab Pulsar, Astrophysics::High Energy Astrophysical Phenomena, Flux, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Pulse (physics), Radio telescope, symbols.namesake, Pulsar, Space and Planetary Science, 0103 physical sciences, Faraday effect, symbols, Large Magellanic Cloud, Astrophysics - High Energy Astrophysical Phenomena, 010303 astronomy & astrophysics
Abstract

PSR J0540$-$6919 is the second-most energetic radio pulsar known and resides in the Large Magellanic Cloud. Like the Crab pulsar it is observed to emit giant radio pulses (GPs). We used the newly-commissioned PTUSE instrument on the MeerKAT radio telescope to search for GPs across three observations. In a total integration time of 5.7 hrs we detected 865 pulses above our 7$\sigma$ threshold. With full polarisation information for a subset of the data, we estimated the Faraday rotation measure, $\rm{RM}=-245.8 \pm 1.0$ rad m$^{-2}$ toward the pulsar. The brightest of these pulses is $\sim$ 60% linearly polarised but the pulse-to-pulse variability in the polarisation fraction is significant. We find that the cumulative GP flux distribution follows a power law distribution with index $-2.75 \pm 0.02$. Although the detected GPs make up only $\sim$ 10% of the mean flux, their average pulse shape is indistinguishable from the integrated pulse profile, and we postulate that there is no underlying emission. The pulses are scattered at L-band frequencies with the brightest pulse exhibiting a scattering time-scale of $\tau = 0.92 \pm 0.02$ ms at 1.2 GHz. We find several of the giants display very narrow-band "flux knots" similar to those seen in many Fast Radio Bursts, which we assert cannot be due to scintillation or plasma lensing. The GP time-of-arrival distribution is found to be Poissonian on all but the shortest time-scales where we find four GPs in six rotations, which if GPs are statistically independent is expected to occur in only 1 of 7000 observations equivalent to our data., Comment: 15 pages, 10 figures

Published
2021

21. The Relativistic Binary Programme on MeerKAT: Science objectives and first results

Author

M. Serylak, Ryan Shannon, D. J. Champion, Matthew Bailes, Lucas Guillemot, Andrew Jameson, Ewan Barr, H. Hu, Ismaël Cognard, Scott M. Ransom, Gemma H. Janssen, Norbert Wex, F. Abbate, Paulo C. C. Freire, L. S. Oswald, Charlotte Sobey, S. Buchner, Ingrid H. Stairs, Daniel J. Reardon, R. Spiewak, Stefan Oslowski, V. Venkatraman Krishnan, Alessandro Ridolfi, T. Gautam, Bettina Posselt, Aditya Parthasarathy, Simon Johnston, Michael Kramer, Michael Keith, Aris Karastergiou, Fernando Camilo, Marcus E. Lower, W. van Straten, M. Burgay, B. Hugo, M. Geyer, A. Possenti, Gilles Theureau, Unité Scientifique de la Station de Nançay (USN), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), and 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)

Subjects
Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, General Relativity and Quantum Cosmology (gr-qc), Astrophysics, 01 natural sciences, General Relativity and Quantum Cosmology, Orbital inclination, Radio telescope, stars: neutron, Pulsar, pulsars: general, 0103 physical sciences, instrumentation: interferometers, 010303 astronomy & astrophysics, Eclipse, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, 010308 nuclear & particles physics, Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy and Astrophysics, Position angle, Light curve, Shapiro delay, Neutron star, gravitation, [SDU]Sciences of the Universe [physics], Space and Planetary Science, [PHYS.GRQC]Physics [physics]/General Relativity and Quantum Cosmology [gr-qc], [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Astrophysics - High Energy Astrophysical Phenomena
Abstract

We describe the ongoing Relativistic Binary programme (RelBin), a part of the MeerTime large survey project with the MeerKAT radio telescope. RelBin is primarily focused on observations of relativistic effects in binary pulsars to enable measurements of neutron star masses and tests of theories of gravity. We selected 25 pulsars as an initial high priority list of targets based on their characteristics and observational history with other telescopes. In this paper, we provide an outline of the programme, present polarisation calibrated pulse profiles for all selected pulsars as a reference catalogue along with updated dispersion measures. We report Faraday rotation measures for 24 pulsars, twelve of which have been measured for the first time. More than a third of our selected pulsars show a flat position angle swing confirming earlier observations. We demonstrate the ability of the Rotating Vector Model (RVM), fitted here to seven binary pulsars, including the Double Pulsar (PSR J0737$-$3039A), to obtain information about the orbital inclination angle. We present a high time resolution light curve of the eclipse of PSR J0737$-$3039A by the companion's magnetosphere, a high-phase resolution position angle swing for PSR J1141$-$6545, an improved detection of the Shapiro delay of PSR J1811$-$2405, and pulse scattering measurements for PSRs J1227$-$6208, J1757$-$1854, and J1811$-$1736. Finally, we demonstrate that timing observations with MeerKAT improve on existing data sets by a factor of, typically, 2-3, sometimes by an order of magnitude., 21 pages 16 figures, published in MNRAS (replaced earlier submission after small changes added in proofs)

Published
2021

22. Measurements of pulse jitter and single-pulse variability in millisecond pulsars using MeerKAT

Author

Stefan Oslowski, Matthew Bailes, Daniel J. Reardon, Andrew Jameson, A. Karastergiou, F. Abbate, Aditya Parthasarathy, V. Venkatraman Krishnan, Fernando Camilo, Simon Johnston, R. Spiewak, S. Buchner, M. Serylak, Ryan Shannon, B. Hugo, M. Geyer, W. van Straten, D. J. Champion, Michael Kramer, Michael Keith, and Timothy T. Pennucci

Subjects
Physics, High Energy Astrophysical Phenomena (astro-ph.HE), 010308 nuclear & particles physics, FOS: Physical sciences, Astronomy and Astrophysics, Context (language use), Astrophysics, 01 natural sciences, Pulse (physics), Radio telescope, Pulsar, Space and Planetary Science, Millisecond pulsar, 0103 physical sciences, Sensitivity (control systems), Astrophysics - High Energy Astrophysical Phenomena, 010303 astronomy & astrophysics, Phenomenology (particle physics), Jitter
Abstract

Using the state-of-the-art SKA precursor, the MeerKAT radio telescope, we explore the limits to precision pulsar timing of millisecond pulsars achievable due to pulse stochasticity (jitter). We report new jitter measurements in 15 of the 29 pulsars in our sample and find that the levels of jitter can vary dramatically between them. For some, like the 2.2~ms pulsar PSR J2241--5236, we measure an implied jitter of just $\sim$ 4~ns/hr, while others like the 3.9~ms PSR J0636--3044 are limited to $\sim$ 100 ns/hr. While it is well known that jitter plays a central role to limiting the precision measurements of arrival times for high signal-to-noise ratio observations, its role in the measurement of dispersion measure (DM) has not been reported, particularly in broad-band observations. Using the exceptional sensitivity of MeerKAT, we explored this on the bright millisecond pulsar PSR J0437--4715 by exploring the DM of literally every pulse. We found that the derived single pulse DMs vary by typically 0.0085 cm$^{-3}$ pc from the mean, and that the best DM estimate is limited by the differential pulse jitter across the band. We postulate that all millisecond pulsars will have their own limit on DM precision which can only be overcome with longer integrations. Using high-time resolution filterbank data of 9 $\mu$s, we also present a statistical analysis of single pulse phenomenology. Finally, we discuss optimization strategies for the MeerKAT pulsar timing program and its role in the context of the International Pulsar Timing Array (IPTA)., Comment: 16 pages, 9 figures

Published
2021

23. 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

24. Anomalous gas in ESO 149-G003: A MeerKAT-16 View

Author

Sharmila Goedhart, Elmar Körding, D. Kleiner, W. J. G. de Blok, Kshitij Thorat, L. A. L. Andati, Patrick Woudt, Steven Bloemen, Dániel Cs. Molnár, J.A. Wang, Marc Klein-Wolt, Eric Maina, L. Sebokolodi, B. Hugo, Gyula I. G. Józsa, S. Makhathini, M. Serylak, S. S. Passmoor, Vanessa McBride, M. Ramatsoku, Paul J. Groot, Paolo Serra, F. M. Maccagni, Oleg Smirnov, Peter Kamphuis, P. M. Vreeswijk, A. J. T. Ramaila, R. S. Le Poole, R. J. Dettmar, Kerry Paterson, D. L. A. Pieterse, and Astronomy

Subjects
media_common.quotation_subject, Astronomy, Minimum mass, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Asymmetry, Radio telescope, 0103 physical sciences, 010303 astronomy & astrophysics, Scaling, Astrophysics::Galaxy Astrophysics, galaxies: kinematics and dynamics, media_common, Physics, 010308 nuclear & particles physics, Astronomy and Astrophysics, galaxies: dwarf, Mass ratio, Astrophysics - Astrophysics of Galaxies, Galaxy, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), Intergalactic travel, Irregular galaxy, galaxies: evolution, galaxies: individual: ESO 149-G003, galaxies: ISM
Abstract

ESO 149-G003 is a close-by, isolated dwarf irregular galaxy. Previous observations with the ATCA indicated the presence of anomalous neutral hydrogen (HI) deviating from the kinematics of a regularly rotating disc. We conducted follow-up observations with the MeerKAT radio telescope during the 16-dish Early Science programme as well as with the MeerLICHT optical telescope. Our more sensitive radio observations confirm the presence of anomalous gas in ESO 149-G003, and further confirm the formerly tentative detection of an extraplanar HI component in the galaxy. Employing a simple tilted-ring model, in which the kinematics is determined with only four parameters but including morphological asymmetries, we reproduce the galaxy's morphology, which shows a high degree of asymmetry. By comparing our model with the observed HI, we find that in our model we cannot account for a significant (but not dominant) fraction of the gas. From the differences between our model and the observed data cube we estimate that at least 7%-8% of the HI in the galaxy exhibits anomalous kinematics, while we estimate a minimum mass fraction of less than 1% for the morphologically confirmed extraplanar component. We investigate a number of global scaling relations and find that, besides being gas-dominated with a neutral gas-to-stellar mass ratio of 1.7, the galaxy does not show any obvious global peculiarities. Given its isolation, as confirmed by optical observations, we conclude that the galaxy is likely currently acquiring neutral gas. It is either re-accreting gas expelled from the galaxy or accreting pristine intergalactic material., 16 pages, 14 figures, MNRAS, Accepted 2020 December 2, in original form 2019 September 18

Published
2021

25. The impact of solar wind variability on pulsar timing

Author

R.-J. Dettmar, Cees Bassa, Gottfried Mann, Caterina Tiburzi, J. Y. Donner, N. K. Porayko, E. van der Wateren, A.-S. Bak Nielsen, Pietro Zucca, Richard Fallows, Jean-Mathias Grießmeier, James M. Anderson, Marcus Brüggen, Christian Vocks, J. Künsemöller, Benedetta Ciardi, Matthias Hoeft, Evan Keane, Gemma H. Janssen, Stefan Oslowski, M. Serylak, G. Shaifullah, Michael Kramer, R. A. Main, Joris P. W. Verbiest, 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), Tiburzi, C, Shaifullah, G, Bassa, C, Zucca, P, Verbiest, J, Porayko, N, Van Der Wateren, E, Fallows, R, Main, R, Janssen, G, Anderson, J, Bak Nielsen, A, Donner, J, Keane, E, Kunsemoller, J, Oslowski, S, Griessmeier, J, Serylak, M, Bruggen, M, Ciardi, B, Dettmar, R, Hoeft, M, Kramer, M, Mann, G, and Vocks, C

Subjects
Astrophysics::High Energy Astrophysical Phenomena, Astronomy, FOS: Physical sciences, Context (language use), Astrophysics, 01 natural sciences, Spherical model, Pulsar, pulsars: general, 0103 physical sciences, 010303 astronomy & astrophysics, ISM: general, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, 010308 nuclear & particles physics, Gravitational wave, Astronomy and Astrophysics, LOFAR, Solar wind, Amplitude, solar wind, gravitational waves, 13. Climate action, Space and Planetary Science, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Astrophysics - High Energy Astrophysical Phenomena, Radio wave
Abstract

High-precision pulsar timing requires accurate corrections for dispersive delays of radio waves, parametrized by the dispersion measure (DM), particularly if these delays are variable in time. In a previous paper we studied the Solar-wind (SW) models used in pulsar timing to mitigate the excess of DM annually induced by the SW, and found these to be insufficient for high-precision pulsar timing. Here we analyze additional pulsar datasets to further investigate which aspects of the SW models currently used in pulsar timing can be readily improved, and at what levels of timing precision SW mitigation is possible. Our goals are to verify: a) whether the data are better described by a spherical model of the SW with a time-variable amplitude rather than a time-invariant one as suggested in literature, b) whether a temporal trend of such a model's amplitudes can be detected. We use the pulsar-timing technique on low-frequency pulsar observations to estimate the DM and quantify how this value changes as the Earth moves around the Sun. Specifically, we monitor the DM in weekly to monthly observations of 14 pulsars taken with LOFAR across time spans of up to 6 years. We develop an informed algorithm to separate the interstellar variations in DM from those caused by the SW and demonstrate the functionality of this algorithm with extensive simulations. Assuming a spherically symmetric model for the SW density, we derive the amplitude of this model for each year of observations. We show that a spherical model with time-variable amplitude models the observations better than a spherical model with constant amplitude, but that both approaches leave significant SW induced delays uncorrected in a number of pulsars in the sample. The amplitude of the spherical model is found to be variable in time, as opposed to what has been previously suggested., 14 pages, 9 figures. Accepted for publication in Astronomy and Astrophysics

Published
2021

26. Eight new millisecond pulsars from the first MeerKAT globular cluster census

Author

L. Vleeschower, Matthew Bailes, S. Buchner, Aditya Parthasarathy, M. Serylak, F. Abbate, T. Gautam, Ryan Shannon, V. Venkatraman Krishnan, Andrew Jameson, Michael Kramer, Scott M. Ransom, Alessandro Corongiu, Alessandro Ridolfi, Weiwei Chen, Aris Karastergiou, M. Geyer, Ramesh Karuppusamy, Ewan Barr, A. Possenti, Daniel J. Reardon, P. V. Padmanabh, Benjamin Stappers, Fernando Camilo, R. Spiewak, M. Burgay, Paulo C. C. Freire, and D. J. Champion

Subjects
High Energy Astrophysical Phenomena (astro-ph.HE), Physics, 010308 nuclear & particles physics, Center (category theory), FOS: Physical sciences, White dwarf, Astronomy and Astrophysics, Radius, Astrophysics, 01 natural sciences, Radio telescope, Neutron star, Pulsar, Space and Planetary Science, Millisecond pulsar, Globular cluster, 0103 physical sciences, Astrophysics - High Energy Astrophysical Phenomena, 010303 astronomy & astrophysics
Abstract

We have used the central 44 antennas of the new 64-dish MeerKAT radio telescope array to conduct a deep search for new pulsars in the core of nine globular clusters. This has led to the discovery of eight new millisecond pulsars in six different clusters. Two new binaries, 47 Tuc ac and 47 Tuc ad, are eclipsing "spiders", featuring compact orbits ($\lesssim 0.32$ days), very low-mass companions and regular occultations of their pulsed emission. The other three new binary pulsars (NGC 6624G, M62G, and Ter 5 an) are in wider ($> 0.7$ days) orbits, with companions that are likely to be white dwarfs or neutron stars. NGC 6624G has a large eccentricity of $e\simeq 0.38$, which enabled us to detect the rate of advance of periastron. This suggests that the system is massive, with a total mass of $M{\rm tot} = 2.65 \pm 0.07$ M$_{\odot}$. Likewise, for Ter 5 an, with $e \simeq 0.0066$, we obtain $M{\rm tot}= 2.97 \pm 0.52$ M$_{\odot}$. The other three new discoveries (NGC 6522D, NGC 6624H and NGC 6752F) are faint isolated pulsars. Finally, we have used the whole MeerKAT array and synthesized 288 beams, covering an area of $\sim2$ arcmin in radius around the center of NGC 6624. This has allowed us to localize many of the pulsars in the cluster, demonstrating the beamforming capabilities of the TRAPUM software backend and paving the way for the upcoming MeerKAT globular cluster pulsar survey., 20 pages, 10 figures. Accepted for publication in Monthly Notices of the Royal Astronomical Society

Published
2021
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27. The Thousand-Pulsar-Array programme on MeerKAT II: observing strategy for pulsar monitoring with subarrays

Author

Daniel J. Reardon, Xiaoxi Song, Simon Johnston, M. Serylak, Ryan Shannon, Michael Keith, Matthew Bailes, Andrew Jameson, V. Venkatraman Krishnan, M. Geyer, Aditya Parthasarathy, S. Buchner, Ewan Barr, Patrick Weltevrede, W. van Straten, B. Hugo, R. Spiewak, and Aris Karastergiou

Subjects
High Energy Astrophysical Phenomena (astro-ph.HE), Physics, 010308 nuclear & particles physics, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Instrumentation and Methods for Astrophysics, FOS: Physical sciences, Astronomy, Astronomy and Astrophysics, 01 natural sciences, Shape parameter, Pulse (physics), law.invention, Radio telescope, Telescope, High fidelity, Square kilometre array, Pulsar, Space and Planetary Science, law, 0103 physical sciences, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Instrumentation and Methods for Astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), 010303 astronomy & astrophysics, Noise (radio)
Abstract

The Thousand Pulsar Array (TPA) project currently monitors about 500 pulsars with the sensitive MeerKAT radio telescope by using subarrays to observe multiple sources simultaneously. Here we define the adopted observing strategy, which guarantees that each target is observed long enough to obtain a high fidelity pulse profile, thereby reaching a sufficient precision of a simple pulse shape parameter. This precision is estimated from the contribution of the system noise of the telescope, and the pulse-to-pulse variability of each pulsar, which we quantify under some simplifying assumptions. We test the assumptions and choice of model parameters using data from the MeerKAT 64-dish array, Lovell and Parkes telescopes. We demonstrate that the observing times derived from our method produce high fidelity pulse profiles that meet the needs of the TPA in studying pulse shape variability and pulsar timing. Our method can also be used to compare strategies for observing large numbers of pulsars with telescopes capable of forming multiple subarray configurations. We find that using two 32-dish MeerKAT subarrays is the most efficient strategy for the TPA project. We also find that the ability to observe in different array configurations will become increasingly important for large observing programmes using the Square Kilometre Array telescope., 13 pages, 8 figures. Accepted for publication in MNRAS

Published
2020

28. Pulsars with NenuFAR: backend and pipelines

Author

Cyril Tasse, A. Possenti, Serge Yerin, Siyuan Chen, L. Bondonneau, C. Viou, M. Serylak, G. Shaifullah, Richard Dallier, J. W. McKee, Z. Wu, Julien N. Girard, Baptiste Cecconi, J.-M. Grießmeier, V. I. Kondratiev, M. Tagger, L. Guillemot, M. Brionne, Maura Pilia, R. A. Main, A. Loh, Ismaël Cognard, P. Zarka, Joris P. W. Verbiest, Caterina Tiburzi, Lilian Martin, Carine Briand, Stephane Corbel, A. V. Bilous, G. Theureau, Olaf Wucknitz, 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), Laboratoire Univers et Théories (LUTH (UMR_8102)), 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), 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), Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), Laboratoire de physique subatomique et des technologies associées (SUBATECH), Université de Nantes - Faculté des Sciences et des Techniques, Université de Nantes (UN)-Université de Nantes (UN)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-IMT Atlantique Bretagne-Pays de la Loire (IMT Atlantique), Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT), Galaxies, Etoiles, Physique, Instrumentation (GEPI), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), Netherlands Institute for Radio Astronomy (ASTRON), Max-Planck-Institut für Radioastronomie (MPIFR), INAF - Osservatorio Astronomico di Cagliari (OAC), Istituto Nazionale di Astrofisica (INAF), Universität Bielefeld = Bielefeld University, Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Rhodes University, Grahamstown, Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics (LESIA), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Université de Nantes (UN)-Université de Nantes (UN)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-IMT Atlantique (IMT Atlantique), Bondonneau, L, Griessmeier, J, Theureau, G, Cognard, I, Brionne, M, Kondratiev, V, Bilous, A, Mckee, J, Zarka, P, Viou, C, Guillemot, L, Chen, S, Main, R, Pilia, M, Possenti, A, Serylak, M, Shaifullah, G, Tiburzi, C, Verbiest, J, Wu, Z, Wucknitz, O, Yerin, S, Briand, C, Cecconi, B, Corbel, S, Dallier, R, Girard, J, Loh, A, Martin, L, Tagger, M, Tasse, C, Université d'Orléans (UO)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), 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 - Instrumentation and Detectors, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics, 4/3, 01 natural sciences, frequency: high, Radio telescope, High Energy Physics - Phenomenology (hep-ph), Pulsar, Millisecond pulsar, Observatory, pulsars: general, 0103 physical sciences, site, Instrumentation (computer programming), structure, [PHYS.PHYS.PHYS-INS-DET]Physics [physics]/Physics [physics]/Instrumentation and Detectors [physics.ins-det], 010303 astronomy & astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), pulsar, Physics, radio wave, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], 010308 nuclear & particles physics, Crab Pulsar, Astrophysics::Instrumentation and Methods for Astrophysics, resolution, Astronomy and Astrophysics, LOFAR, Instrumentation and Detectors (physics.ins-det), sensitivity, coherence, observatory, High Energy Physics - Phenomenology, frequency: low, Space and Planetary Science, [PHYS.HPHE]Physics [physics]/High Energy Physics - Phenomenology [hep-ph], dispersion, methods: observational, Astrophysics - Instrumentation and Methods for Astrophysics, performance, Radio wave
Abstract

NenuFAR (New extension in Nan\c{c}ay upgrading LoFAR) is a new radio telescope developed and built on the site of the Nan\c{c}ay Radio Observatory. It is designed to observe the largely unexplored frequency window from 10 to 85\,MHz, offering a high sensitivity across its full bandwidth. NenuFAR has started its "early science" operation in July 2019, with 58\% of its final collecting area being available. Pulsars are one of the major topics for the scientific exploitation of this frequency range and represent an important challenge in terms of instrumentation. Designing instrumentation at these frequencies is complicated by the need to compensate for the effects of both the interstellar medium and the ionosphere on the observed signal. Our real-time pipeline LUPPI (Low frequency Ultimate Pulsar Processing Instrumentation) is able to cope with a high data rate and to provide real-time coherent de-dispersion down to the lowest frequencies reached by NenuFAR (10\,MHz). The full backend functionality is described, as well as the main pulsar observing modes (folded, single-pulse, waveform, and dynamic spectrum). This instrumentation allowed us to detect 172 pulsars in our first targeted search below 85\,MHz, including 10 millisecond pulsars (6 of which detected for the first time below 100 MHz). We also present some of the "early science" results of NenuFAR on pulsars: a high frequency resolution mapping of PSR B1919$+$21's emission profile and a detailed observation of single-pulse sub-structures from PSR~B0809$+$74 down to 16\,MHz, the high rate of giant-pulse emission from the Crab pulsar detected at 68.7\,MHz (43 events/min), and the illustration of the very good timing performance of the instrumentation, allowing us to study dispersion measure variations in great detail., Comment: 13 pages, 14 figures, submitted to A&A

Published
2020

29. The Thousand-Pulsar-Array programme on MeerKAT. I: Science objectives and first results

Author

Aris Karastergiou, Ryan Shannon, Simon Johnston, Renée Spiewak, Fabian Jankowski, M. Geyer, Michael Kramer, Andrew Jameson, Alessandro Ridolfi, S. Buchner, Patrick Weltevrede, B. Hugo, Michael Keith, M. Serylak, Daniel J. Reardon, Bettina Posselt, Matthew Bailes, L. S. Oswald, Aditya Parthasarathy, Andrzej Szary, X. Song, B. W. Meyers, W. van Straten, Fernando Camilo, Federico Abbate, Charlotte Sobey, V. Venkatraman Krishnan, J. van Leeuwen, and High Energy Astrophys. & Astropart. Phys (API, FNWI)

Subjects
Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Magnetosphere, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, 7. Clean energy, law.invention, Telescope, symbols.namesake, Pulsar, law, 0103 physical sciences, Faraday effect, Wide band, Instrumentation and Methods for Astrophysics (astro-ph.IM), 010303 astronomy & astrophysics, Solar and Stellar Astrophysics (astro-ph.SR), High Energy Astrophysical Phenomena (astro-ph.HE), Physics, 010308 nuclear & particles physics, Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy, Astronomy and Astrophysics, Pulse (physics), Interstellar medium, Interferometry, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, symbols, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Instrumentation and Methods for Astrophysics
Abstract

We report here on initial results from the Thousand Pulsar Array (TPA) programme, part of the Large Survey Project "MeerTime" on the MeerKAT telescope. The interferometer is used in tied-array mode in the band from 856 to 1712~MHz, and the wide band coupled with the large collecting area and low receiver temperature make it an excellent telescope for the study of radio pulsars. The TPA is a 5 year project which aims to observe (a) more than 1000 pulsars to obtain high-fidelity pulse profiles, (b) some 500 of these pulsars over multiple epochs, (c) long sequences of single-pulse trains from several hundred pulsars. The scientific outcomes from the programme will include determination of pulsar geometries, the location of the radio emission within the pulsar magnetosphere, the connection between the magnetosphere and the crust and core of the star, tighter constraints on the nature of the radio emission itself as well as interstellar medium studies. First results presented here include updated dispersion measures, 26 pulsars with Faraday rotation measures derived for the first time and a description of interesting emission phenomena observed thus far., Accepted by MNRAS

Published
2020

30. A census of the pulsar population observed with the international LOFAR station FR606 at low frequencies (25-80 MHz)

Author

V. I. Kondratiev, Gilles Theureau, L. Bondonneau, Anna V. Bilous, Andrew Lyne, M. Serylak, Jean-Mathias Grießmeier, Michael Keith, Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National d’Études Spatiales [Paris] (CNES), Unité Scientifique de la Station de Nançay (USN), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO), Laboratoire Univers et Théories (LUTH (UMR_8102)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7), 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), 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), and PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Astrophysics::High Energy Astrophysical Phenomena, Population, general [Pulsars], FOS: Physical sciences, Context (language use), Astrophysics, Low frequency, 01 natural sciences, Declination, Spectral line, Pulsar, pulsars: general, 0103 physical sciences, [PHYS.PHYS.PHYS-INS-DET]Physics [physics]/Physics [physics]/Instrumentation and Detectors [physics.ins-det], education, 010303 astronomy & astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), Solar and Stellar Astrophysics (astro-ph.SR), ISM: general, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), [PHYS]Physics [physics], education.field_of_study, general [ISM], 010308 nuclear & particles physics, Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy and Astrophysics, telescopes, LOFAR, Interstellar medium, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, [SDU]Sciences of the Universe [physics], Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Instrumentation and Methods for Astrophysics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Telescopes
Abstract

International audience; Context. To date, only 69 pulsars have been identified with a detected pulsed radio emission below 100 MHz. A LOFAR-core LBA census and a dedicated campaign with the Nançay LOFAR station in stand-alone mode were carried out in the years 2014–2017 in order to extend the known population in this frequency range.Aims. In this paper, we aim to extend the sample of known radio pulsars at low frequencies and to produce a catalogue in the frequency range of 25–80 MHz. This will allow future studies to probe the local Galactic pulsar population, in addition to helping explain their emission mechanism, better characterising the low-frequency turnover in their spectra, and obtaining new information about the interstellar medium through the study of dispersion, scattering, and scintillation.Methods. We observed 102 pulsars that are known to emit radio pulses below 200 MHz and with declination above −30°. We used the Low Band Antennas (LBA) of the LOw Frequency ARray (LOFAR) international station FR606 at the Nançay Radio Observatory in stand-alone mode, recording data between 25 and 80 MHz.Results. Out of our sample of 102 pulsars, we detected 64. We confirmed the existence of ten pulsars detected below 100 MHz by the LOFAR LBA census for the first time (Bilous et al. 2020, A&A, 635, A75) and we added two more pulsars that had never before been detected in this frequency range. We provided average pulse profiles, DM values, and mean flux densities (or upper limits in the case of non-detections). The comparison with previously published results allows us to identify a hitherto unknown spectral turnover for five pulsars, confirming the expectation that spectral turnovers are a widespread phenomenon.Key words: pulsars: general / telescopes / ISM: general⋆ Data tables and the reduced pulse profiles are only 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/A76

Published
2020

31. Dispersion measure variability for 36 millisecond pulsars at 150 MHz with LOFAR

Author

Rene P. Breton, C. Vocks, A. V. Bilous, Stefan Oslowski, J. Y. Donner, J. Künsemöller, Michael Kramer, A.-S. Bak Nielsen, Evan Keane, James M. Anderson, V. I. Kondratiev, M. Serylak, Caterina Tiburzi, B. Ciardi, O. Wucknitz, Marcus Brüggen, Charlotte Sobey, J. van Leeuwen, J. W. McKee, Joris P. W. Verbiest, Matthias Hoeft, 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)-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), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), CNRS-INSU, and European Project: 617199,EC:FP7:ERC,ERC-2013-CoG,ALERT(2014)

Subjects
ISM: structure, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics, 01 natural sciences, law.invention, Telescope, Pulsar, Millisecond pulsar, law, pulsars: general, 0103 physical sciences, Dispersion (optics), 010303 astronomy & astrophysics, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), [PHYS]Physics [physics], 010308 nuclear & particles physics, Gravitational wave, Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy and Astrophysics, LOFAR, Astrophysics - Astrophysics of Galaxies, gravitational waves, Space and Planetary Science, [SDU]Sciences of the Universe [physics], Astrophysics of Galaxies (astro-ph.GA), ddc:520, Radio frequency, Astrophysics - High Energy Astrophysical Phenomena, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Noise (radio)
Abstract

Radio pulses from pulsars are affected by plasma dispersion, which results in a frequency-dependent propagation delay. Variations in the magnitude of this effect lead to an additional source of red noise in pulsar timing experiments, including pulsar timing arrays that aim to detect nanohertz gravitational waves. We aim to quantify the time-variable dispersion with much improved precision and characterise the spectrum of these variations. We use the pulsar timing technique to obtain highly precise dispersion measure (DM) time series. Our dataset consists of observations of 36 millisecond pulsars, which were observed for up to 7.1 years with the LOFAR telescope at a centre frequency of ~150 MHz. Seventeen of these sources were observed with a weekly cadence, while the rest were observed at monthly cadence. We achieve a median DM precision of the order of 10^-5 cm^-3 pc for a significant fraction of our sources. We detect significant variations of the DM in all pulsars with a median DM uncertainty of less than 2x10^-4 cm^-3 pc. The noise contribution to pulsar timing experiments at higher frequencies is calculated to be at a level of 0.1-10 us at 1.4 GHz over a timespan of a few years, which is in many cases larger than the typical timing precision of 1 us or better that PTAs aim for. We found no evidence for a dependence of DM on radio frequency for any of the sources in our sample. The DM time series we obtained using LOFAR could in principle be used to correct higher-frequency data for the variations of the dispersive delay. However, there is currently the practical restriction that pulsars tend to provide either highly precise times of arrival (ToAs) at 1.4 GHz or a high DM precision at low frequencies, but not both, due to spectral properties. Combining the higher-frequency ToAs with those from LOFAR to measure the infinite-frequency ToA and DM would improve the result., Comment: 16 pages, 8 figures, 2 tables

Published
2020

32. Giant pulses from J1823-3021A observed with the MeerKAT telescope

Author

S. Buchner, Renée Spiewak, Matthew Bailes, V. Venkatraman Krishnan, Andrew Jameson, Fernando Camilo, Paulo C. C. Freire, F. Abbate, A. Possenti, Michael Kramer, M. Geyer, M. Serylak, Benjamin Stappers, and Alessandro Ridolfi

Subjects
Physics, High Energy Astrophysical Phenomena (astro-ph.HE), Spectral index, 010504 meteorology & atmospheric sciences, Linear polarization, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Polarization (waves), 01 natural sciences, Radio telescope, Pulsar, 13. Climate action, Space and Planetary Science, Millisecond pulsar, Globular cluster, 0103 physical sciences, Astrophysics::Earth and Planetary Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, 010303 astronomy & astrophysics, Circular polarization, Astrophysics::Galaxy Astrophysics, 0105 earth and related environmental sciences
Abstract

The millisecond pulsar J1823-3021A is a very active giant pulse emitter in the globular cluster NGC 6624. New observations with the MeerKAT radio telescope have revealed 14350 giant pulses over 5 hours of integration time, with an average wait time of about 1 second between giant pulses. The giant pulses occur in phases compatible with the ordinary radio emission, follow a power-law distribution with an index of -2.63 $\pm$ 0.02 and contribute 4 percent of the total integrated flux. The spectral index of the giant pulses follows a Gaussian distribution centered around -1.9 with a standard deviation of 0.6 and is on average flatter than the integrated emission, which has a spectral index of -2.81 $\pm$ 0.02. The waiting times between the GPs are accurately described by a Poissonian distribution, suggesting that the time of occurrence of a GP is independent from the times of occurrence of other GPs. 76 GPs show multiple peaks within the same rotation, a rate that is also compatible with the mutual independence of the GP times of occurrence. We studied the polarization properties of the giant pulses finding, on average, linear polarization only at the 1 percent level and circular polarization at the 3 percent level, similar to the polarization percentages of the total integrated emission. In 4 cases it was possible to measure the RM of the GPs which are highly variable and, in two cases, is inconsistent with the mean RM of the total integrated pulsar signal., Comment: Accepted for publication in MNRAS. 8 Pages, 11 Figures

Published
2020
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33. A LOFAR observation of ionospheric scintillation from two simultaneous travelling ionospheric disturbances

Author

M. Iacobelli, M. A. Garrett, I. Max Avruch, Bartosz Dabrowski, Hanna Rothkaehl, Richard Fallows, Michiel van Haarlem, Olaf Wucknitz, A. W. Gunst, Tom Allbrook, Jean Matthias Grießmeier, Harvey Butcher, Christian Vocks, Jörg R. Hörandel, Vishambhar Pandey, Léon V. E. Koopmans, Anna Nelles, Biagio Forte, Barbara Matyjasiak, P. Maat, Gareth Dorrian, Thomas M. O. Franzen, M. Ruiter, Ashish Asgekar, Oleg Smirnov, Ilse van Bemmel, Antonia Rowlinson, Matthijs H. D. van der Wiel, M. Serylak, Ivan Astin, Dominik J. Schwarz, Mark J. Bentum, Arnold van Ardenne, Matthias Hoeft, Gottfried Mann, S. Duscha, Alex Arnold, Huib Intema, H. Paas, S. Damstra, Francesco de Gasperin, James M. Anderson, Jochen Eislöffel, Maaijke Mevius, Benedetta Ciardi, Andrzej Krankowski, M. Carmen Toribio, Alan Wood, Satyendra Thoudam, Aleksander Shulevski, Mario M. Bisi, Ralph A. M. J. Wijers, Pietro Zucca, Philippe Zarka, Wolfgang Reich, Marian Soida, Rene C. Vermeulen, Matthias Steinmetz, Netherlands Institute for Radio Astronomy (ASTRON), Environmental Systems Science Centre [Reading] (ESSC), University of Reading (UOR), Space Research Centre of Polish Academy of Sciences (CBK), Polska Akademia Nauk = Polish Academy of Sciences (PAN), Department of Computer Science [Chapel Hill], University of North Carolina [Chapel Hill] (UNC), University of North Carolina System (UNC)-University of North Carolina System (UNC), Eindhoven Technical University, STFC Rutherford Appleton Laboratory (RAL), Science and Technology Facilities Council (STFC), 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), 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), Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), Radboud university [Nijmegen], Leiden Observatory [Leiden], Universiteit Leiden [Leiden], Commonwealth Scientific and Industrial Research Organisation [Canberra] (CSIRO), SKA South Africa, Ska South Africa, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), and Astronomy

Subjects
Atmospheric Science, 010504 meteorology & atmospheric sciences, Astronomy, FOS: Physical sciences, Instability mechanisms, lcsh:QC851-999, 01 natural sciences, Physics::Geophysics, Physics - Geophysics, travelling ionospheric disturbances, Interplanetary scintillation, Physics - Space Physics, Ionospheric scintillation, 0103 physical sciences, ddc:550, Gravity wave, Travelling ionospheric disturbances, 010303 astronomy & astrophysics, Physics::Atmospheric and Oceanic Physics, 0105 earth and related environmental sciences, Physics, [PHYS]Physics [physics], Earth and Planetary Astrophysics (astro-ph.EP), Scintillation, Scattering, LOFAR, Geodesy, Space Physics (physics.space-ph), Geophysics (physics.geo-ph), instability mechanisms, Earth's magnetic field, 13. Climate action, Space and Planetary Science, [SDU]Sciences of the Universe [physics], Physics::Space Physics, lcsh:Meteorology. Climatology, Ionosphere, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Ionosonde, Astrophysics - Earth and Planetary Astrophysics
Abstract

This paper presents the results from one of the first observations of ionospheric scintillation taken using the Low-Frequency Array (LOFAR). The observation was of the strong natural radio source Cas A, taken overnight on 18-19 August 2013, and exhibited moderately strong scattering effects in dynamic spectra of intensity received across an observing bandwidth of 10-80MHz. Delay-Doppler spectra (the 2-D FFT of the dynamic spectrum) from the first hour of observation showed two discrete parabolic arcs, one with a steep curvature and the other shallow, which can be used to provide estimates of the distance to, and velocity of, the scattering plasma. A cross-correlation analysis of data received by the dense array of stations in the LOFAR "core" reveals two different velocities in the scintillation pattern: a primary velocity of ~30m/s with a north-west to south-east direction, associated with the steep parabolic arc and a scattering altitude in the F-region or higher, and a secondary velocity of ~110m/s with a north-east to south-west direction, associated with the shallow arc and a scattering altitude in the D-region. Geomagnetic activity was low in the mid-latitudes at the time, but a weak sub-storm at high latitudes reached its peak at the start of the observation. An analysis of Global Navigation Satellite Systems (GNSS) and ionosonde data from the time reveals a larger-scale travelling ionospheric disturbance (TID), possibly the result of the high-latitude activity, travelling in the north-west to south-east direction, and, simultaneously, a smaller--scale TID travelling in a north-east to south-west direction, which could be associated with atmospheric gravity wave activity. The LOFAR observation shows scattering from both TIDs, at different altitudes and propagating in different directions. To the best of our knowledge this is the first time that such a phenomenon has been reported., Comment: 24 pages, 16 figures. Accepted for open-access publication in the Journal of Space Weather and Space Climate. For associated movie file, see https://www.swsc-journal.org/10.1051/swsc/2020010/olm

Published
2020

34. Simultaneous multi-telescope observations of FRB 121102

Author

Maura Pilia, Kaustubh Rajwade, Fabian Jankowski, Patrick Woudt, Emma Platts, Alessandro Ridolfi, S. Sanidas, John Hoang, Laura Driessen, Benjamin Stappers, Rob Fender, Michael Kramer, M. Serylak, M. Burgay, Ewan Barr, Ismaël Cognard, Jingwen Wu, Vincent Morello, A. Possenti, Mechiel Christiaan Bezuidenhout, Amanda Weltman, G. H. Hilmarsson, D. M. Horn, L. Rhodes, Mateusz Malenta, Duncan R. Lorimer, Laura Spitler, T. D. Abbott, Weiwei Chen, L. J. Townsend, M. Caleb, S. Buchner, 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), and Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)

Subjects
FOS: Physical sciences, 01 natural sciences, law.invention, Radio telescope, Telescope, surveys, law, 0103 physical sciences, Wide band, [PHYS.PHYS.PHYS-INS-DET]Physics [physics]/Physics [physics]/Instrumentation and Detectors [physics.ins-det], instrumentation: interferometers, 010303 astronomy & astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), Physics, High Energy Astrophysical Phenomena (astro-ph.HE), 010308 nuclear & particles physics, Single pulse, Astronomy, Astronomy and Astrophysics, methods: data analysis, Space and Planetary Science, Intergalactic medium, transients: fast radio bursts, intergalactic medium, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Instrumentation and Methods for Astrophysics
Abstract

We present 11 detections of FRB 121102 in ~3 hours of observations during its 'active' period on the 10th of September 2019. The detections were made using the newly deployed MeerTRAP system and single pulse detection pipeline at the MeerKAT radio telescope in South Africa. Fortuitously, the Nancay radio telescope observations on this day overlapped with the last hour of MeerKAT observations and resulted in 4 simultaneous detections. The observations with MeerKAT's wide band receiver, which extends down to relatively low frequencies (900-1670 MHz usable L-band range), have allowed us to get a detailed look at the complex frequency structure, intensity variations and frequency-dependent sub-pulse drifting. The drift rates we measure for the full-band and sub-banded data are consistent with those published between 600-6500 MHz with a slope of -0.147 +/- 0.014 ms^-1. Two of the detected bursts exhibit fainter 'precursors' separated from the brighter main pulse by ~28 ms and ~34 ms. A follow-up multi-telescope campaign on the 6th and 8th October 2019 to better understand these frequency drifts and structures over a wide and continuous band was undertaken. No detections resulted, indicating that the source was 'inactive' over a broad frequency range during this time., Accepted for publication in MNRAS

Published
2020

35. 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

36. The MeerKAT Galaxy Cluster Legacy Survey

Author

K. Knowles, W. D. Cotton, L. Rudnick, F. Camilo, S. Goedhart, R. Deane, M. Ramatsoku, M. F. Bietenholz, M. Brüggen, C. Button, H. Chen, J. O. Chibueze, T. E. Clarke, F. de Gasperin, R. Ianjamasimanana, G. I. G. Józsa, M. Hilton, K. C. Kesebonye, K. Kolokythas, R. C. Kraan-Korteweg, G. Lawrie, M. Lochner, S. I. Loubser, P. Marchegiani, N. Mhlahlo, K. Moodley, E. Murphy, B. Namumba, N. Oozeer, V. Parekh, D. S. Pillay, S. S. Passmoor, A. J. T. Ramaila, S. Ranchod, E. Retana-Montenegro, L. Sebokolodi, S. P. Sikhosana, O. Smirnov, K. Thorat, T. Venturi, T. D. Abbott, R. M. Adam, G. Adams, M. A. Aldera, E. F. Bauermeister, T. G. H. Bennett, W. A. Bode, D. H. Botha, A. G. Botha, L. R. S. Brederode, S. Buchner, J. P. Burger, T. Cheetham, D. I. L. de Villiers, M. A. Dikgale-Mahlakoana, L. J. du Toit, S. W. P. Esterhuyse, G. Fadana, B. L. Fanaroff, S. Fataar, A. R. Foley, D. J. Fourie, B. S. Frank, R. R. G. Gamatham, T. G. Gatsi, M. Geyer, M. Gouws, S. C. Gumede, I. Heywood, M. J. Hlakola, A. Hokwana, S. W. Hoosen, D. M. Horn, J. M. G. Horrell, B. V. Hugo, A. R. Isaacson, J. L. Jonas, J. D. B. Jordaan, A. F. Joubert, R. P. M. Julie, F. B. Kapp, V. A. Kasper, J. S. Kenyon, P. P. A. Kotzé, A. G. Kotze, N. Kriek, H. Kriel, V. K. Krishnan, T. W. Kusel, L. S. Legodi, R. Lehmensiek, D. Liebenberg, R. T. Lord, B. M. Lunsky, K. Madisa, L. G. Magnus, J. P. L. Main, A. Makhaba, S. Makhathini, J. A. Malan, J. R. Manley, S. J. Marais, M. D. J. Maree, A. Martens, T. Mauch, K. McAlpine, B. C. Merry, R. P. Millenaar, O. J. Mokone, T. E. Monama, M. C. Mphego, W. S. New, B. Ngcebetsha, K. J. Ngoasheng, M. T. Ockards, A. J. Otto, A. A. Patel, A. Peens-Hough, S. J. Perkins, N. M. Ramanujam, Z. R. Ramudzuli, S. M. Ratcliffe, R. Renil, A. Robyntjies, A. N. Rust, S. Salie, N. Sambu, C. T. G. Schollar, L. C. Schwardt, R. L. Schwartz, M. Serylak, R. Siebrits, S. K. Sirothia, M. Slabber, L. Sofeya, B. Taljaard, C. Tasse, A. J. Tiplady, O. Toruvanda, S. N. Twum, T. J. van Balla, A. van der Byl, C. van der Merwe, C. L. van Dyk, V. Van Tonder, R. Van Wyk, A. J. Venter, M. Venter, M. G. Welz, L. P. Williams, and B. Xaia

Subjects
Physics, Cosmology and Nongalactic Astrophysics (astro-ph.CO), Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, Astrophysics - Astrophysics of Galaxies, Galaxy cluster, Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract

MeerKAT's large number of antennas, spanning 8 km with a densely packed 1 km core, create a powerful instrument for wide-area surveys, with high sensitivity over a wide range of angular scales. The MeerKAT Galaxy Cluster Legacy Survey (MGCLS) is a programme of long-track MeerKAT L-band (900-1670 MHz) observations of 115 galaxy clusters, observed for $\sim$6-10 hours each in full polarisation. The first legacy product data release (DR1), made available with this paper, includes the MeerKAT visibilities, basic image cubes at $\sim$8" resolution, and enhanced spectral and polarisation image cubes at $\sim$8" and 15" resolutions. Typical sensitivities for the full-resolution MGCLS image products are $\sim$3-5 {\mu}Jy/beam. The basic cubes are full-field and span 4 deg^2. The enhanced products consist of the inner 1.44 deg^2 field of view, corrected for the primary beam. The survey is fully sensitive to structures up to $\sim$10' scales and the wide bandwidth allows spectral and Faraday rotation mapping. HI mapping at 209 kHz resolution can be done at $0, Comment: 43 pages, 33 figures, 6 tables. Accepted for publication in Astronomy and Astrophysics

Published
2022

37. Discovery of synchronous X-ray and radio moding of PSR B0823+26

Author

Caterina Tiburzi, J.-M. Grießmeier, A. Horneffer, W. Hermsen, Rahul Basu, G. A. E. Wright, Joanna M. Rankin, Dipanjan Mitra, Wynn C. G. Ho, L. Kuiper, Jason W. T. Hessels, M. Serylak, Benjamin Stappers, High Energy Astrophys. & Astropart. Phys (API, FNWI), Unité Scientifique de la Station de Nançay (USN), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), 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), and PSL Research University (PSL)-PSL Research University (PSL)-Centre National d’Études Spatiales [Paris] (CNES)

Subjects
Astrophysics::High Energy Astrophysical Phenomena, Phase (waves), FOS: Physical sciences, Flux, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, Low frequency, 01 natural sciences, stars: neutron, pulsars: general, Ionization, 0103 physical sciences, PSR B0943+10, 010306 general physics, 010303 astronomy & astrophysics, X-rays: individual: PSR B0823+26, Astrophysics::Galaxy Astrophysics, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, Giant Metrewave Radio Telescope, Line-of-sight, Accretion (meteorology), Astronomy and Astrophysics, Interstellar medium, [SDU]Sciences of the Universe [physics], 13. Climate action, Space and Planetary Science, PSR B1822−09, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Astrophysics - High Energy Astrophysical Phenomena
Abstract

Simultaneous observations of PSR B0823+26 with ESA's XMM-Newton, the Giant Metrewave Radio Telescope and international stations of the Low Frequency Array revealed synchronous X-ray/radio switching between a radio-bright (B) mode and a radio-quiet (Q) mode. During the B mode we detected PSR B0823+26 in 0.2$-$2 keV X-rays and discovered pulsed emission with a broad sinusoidal pulse, lagging the radio main pulse by 0.208 $\pm$ 0.012 in phase, with high pulsed fraction of 70$-$80%. During the Q mode PSR B0823+26 was not detected in X-rays (2 $\sigma$ upper limit a factor ~9 below the B-mode flux). The total X-ray spectrum, pulse profile and pulsed fraction can globally be reproduced with a magnetized partially ionized hydrogen atmosphere model with three emission components: a primary small hot spot ($T$$\sim$3.6$\times10^6$ K, $R$$\sim$17 m), a larger cooler concentric ring ($T$$\sim$1.1$\times10^6$ K, $R$$\sim$280 m) and an antipodal hot spot ($T$$\sim$1.1$\times10^6 $ K, $R$$\sim$100 m), for the angle between the rotation axis and line of sight direction $\sim66^\circ$. The latter is in conflict with the radio derived value of $(84\pm0.7)^\circ$. The average X-ray flux within hours-long B-mode intervals varied by a factor $\pm$20%, possibly correlated with variations in the frequency and lengths of short radio nulls or short durations of weak emission. The correlated X-ray/radio moding of PSR B0823+26 is compared with the anti-correlated moding of PSR B0943+10, and the lack of X-ray moding of PSR B1822-09. We speculate that the X-ray/radio switches of PSR B0823+26 are due to variations in the rate of accretion of material from the interstellar medium through which it is passing., Comment: 16 pages, 11 figures

Published
2018

38. Inflation of 430-parsec bipolar radio bubbles in the Galactic Centre by an energetic event

Author

Jasper Horrell, M. Serylak, T. D. Abbott, P. P. A. Kotzé, J. P. Burger, L. G. Magnus, A. A. Pate, P. S. Swart, A. Loots, S. Tshongweni, A. van der Byl, S. Buchner, Farhad Yusef-Zadeh, Jason Manley, T. W. Kusel, R. Renil, T. J. van Balla, D. H. Botha, A. R. Foley, N. Mnyandu, O. Mahgoub, A. G. Botha, B. M. Lunsky, L. C. Schwardt, Bruce Merry, A. J. Tiplad, C. J. Hoek, R. Siebrits, Dirk I. L. de Villiers, C. L. van Dyk, T. Cheetham, J. A. Malan, C.G. Van der Merwe, D. M. Horn, S. Salie, T. E. Monama, A. R. Isaacson, I. P. T. Moeng, Kshitij Thorat, E. F. Bauermeister, Roy Booth, F. Kapp, B. L. Fanaroff, Simon Perkins, M. C. Mphego, A. Rust, V. Van Tonder, W. S. New, Oleg Smirnov, S. Gounden, H. Kriel, J. D. B. L. Jordaan, M. A. Dikgale-Mahlakoana, R. T. Lord, L. J. du Toit, B. Ngcebetsha, S. W. P. Esterhuyse, P. Macfarlane, Sharmila Goedhart, D. T. Taylor, Justin L. Jonas, R. van Rooyen, C. Magozore, M. J. Hlakola, Dehann Fourie, Robert Lehmensiek, A. F. Joubert, Fernando Camilo, B. H. Wallace, D. Liebenberg, R. van Wyk, R. R. G. Gamatham, Gyula I. G. Józsa, Nadeem Oozeer, J. S. Kenyon, R. D. Malgas, Robert P. Millenaar, Matthys Maree, A. Hokwana, J. M. Chalmers, C. Tasse, L. P. Williams, R. M. Adam, Z. B. Brits, L. R. S. Brederode, W. D. Cotton, J. P. L. Main, M. G. Welz, B. Hugo, A. Peens-Hough, L. Sofeya, Ian Heywood, S. Ratcliffe, I. P. Theron, S. S. Passmoor, M. A. Aldera, A. J. Otto, S. K. Sirothia, R. P. M. Julie, Galaxies, Etoiles, Physique, Instrumentation (GEPI), 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)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Active galactic nucleus, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Cosmic ray, Context (language use), Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Relativistic particle, 0103 physical sciences, Disc, 010306 general physics, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, ComputingMilieux_MISCELLANEOUS, Physics, [PHYS]Physics [physics], Supermassive black hole, Multidisciplinary, Star formation, Galactic plane, Astrophysics - Astrophysics of Galaxies, 13. Climate action, Astronomy and astrophysics, Astrophysics of Galaxies (astro-ph.GA), [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract

The Galactic Centre contains a supermassive black hole with a mass of 4 million suns within an environment that differs markedly from that of the Galactic disk. While the black hole is essentially quiescent in the broader context of active galactic nuclei, X-ray observations have provided evidence for energetic outbursts from its surroundings. Also, while the levels of star formation in the Galactic Centre have been approximately constant over the last few hundred Myr, there is evidence of elevated short-duration bursts, strongly influenced by interaction of the black hole with the enhanced gas density present within the ring-like Central Molecular Zone at Galactic longitude |l| < 0.7 degrees and latitude |b| < 0.2 degrees. The inner 200 pc region is characterized by large amounts of warm molecular gas, a high cosmic ray ionization rate, unusual gas chemistry, enhanced synchrotron emission, and a multitude of radio-emitting magnetised filaments, the origin of which has not been established. Here we report radio imaging that reveals bipolar bubbles spanning 1 degree x 3 degrees (140 parsecs x 430 parsecs), extending above and below the Galactic plane and apparently associated with the Galactic Centre. The structure is edge-brightened and bounded, with symmetry implying creation by an energetic event in the Galactic Centre. We estimate the age of the bubbles to be a few million years, with a total energy of 7 x 10^52 ergs. We postulate that the progenitor event was a major contributor to the increased cosmic-ray density in the Galactic Centre, and is in turn the principal source of the relativistic particles required to power the synchrotron emission of the radio filaments within and in the vicinity of the bubble cavities., 25 pages, 3 figures, 3 tables, authors' version of a Letter published in Nature on 11 September 2019

Published
2019

39. 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

40. First detection of frequency-dependent, time-variable dispersion measures

Author

Stefan Oslowski, J. Künsemöller, Arpad Miskolczi, Joris P. W. Verbiest, Jean-Mathias Grießmeier, Matthias Hoeft, Caterina Tiburzi, J. M. Anderson, A. Horneffer, Michael Kramer, D. Michilli, Jason W. T. Hessels, M. Serylak, J. Y. Donner, 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), 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), and High Energy Astrophys. & Astropart. Phys (API, FNWI)

Subjects
Frequency band, Astrophysics::High Energy Astrophysical Phenomena, ISM: structure, FOS: Physical sciences, Context (language use), Electron, Astrophysics, 01 natural sciences, ISM: clouds, 0103 physical sciences, Dispersion (optics), 010303 astronomy & astrophysics, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), Line-of-sight, 010308 nuclear & particles physics, Scattering, pulsars: individual: PSR J2219+4754, Astronomy and Astrophysics, LOFAR, Refraction, Astrophysics - Astrophysics of Galaxies, 13. Climate action, Space and Planetary Science, [SDU]Sciences of the Universe [physics], Astrophysics of Galaxies (astro-ph.GA), [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Astrophysics - High Energy Astrophysical Phenomena
Abstract

Context. High-precision pulsar-timing experiments are affected by temporal variations of the Dispersion Measure (DM), which are related to spatial variations in the interstellar electron content. Correcting for DM variations relies on the cold-plasma dispersion law which states that the dispersive delay varies with the squared inverse of the observing frequency. This may however give incorrect measurements if the probed electron content (and therefore the DM) varies with observing frequency, as is predicted theoretically. Aims. We study small-scale density variations in the ionised interstellar medium. These structures may lead to frequency-dependent DMs in pulsar signals and could inhibit the use of lower-frequency pulsar observations to correct time-variable interstellar dispersion in higher-frequency pulsar-timing data. Methods. We used high-cadence, low-frequency observations with three stations from the German LOng-Wavelength (GLOW) consortium, which are part of the LOw Frequency ARray (LOFAR). Specifically, 3.5 years of weekly observations of PSR J2219+4754 are presented. Results. We present the first detection of frequency-dependent DMs towards any interstellar object and a precise multi-year time-series of the time- and frequency-dependence of the measured DMs. The observed DM variability is significant and may be caused by extreme scattering events. Potential causes for frequency-dependent DMs are quantified and evaluated. Conclusions. We conclude that frequency-dependence of DMs has been reliably detected and is caused by small-scale (up to 10s of AUs) but steep density variations in the interstellar electron content. We find that long-term trends in DM variability equally affect DMs measured at both ends of our frequency band and hence the negative impact on long-term high-precision timing projects is expected to be limited., to be published in A&A (accepted 2019-02-06), 11 pages, 7 figures, update: A&A language editing, typos

Published
2019

41. The 1.28 GHz MeerKAT DEEP2 Image

Author

K. M. B. Asad, T. E. Monama, E. F. Bauermeister, Bruce Merry, O. Toruvanda, S. J. Marais, B. M. Lunsky, L. C. Schwardt, H. Bester, H. Kriel, M. Geyer, S. February, B. H. Wallace, M. Serylak, S. N. Twum, N. Kriek, B. Taljaard, M. A. Dikgale-Mahlakoana, W. S. New, K. Madisa, R. M. Adam, Oleg Smirnov, S. Fataar, R. Millenaar, Z. R. Ramudzuli, S. Gounden, I. P. Theron, K. J. Ngoasheng, Z. B. Brits, J. Horrell, G. Stone, D. H. Botha, T. W. Kusel, B. Xaia, M. J. Hlakola, B. S. Frank, S. W. P. Esterhuyse, Jason Manley, James J. Condon, A. Robyntjies, J. A. Malan, Gyula I. G. Józsa, A. A. Patel, R. R. G. Gamatham, Justin L. Jonas, S. C. Gumede, R. Siebrits, A. J. T. Ramaila, M. T. O. Ockards, Nadeem Oozeer, J. P. Burger, A. Loots, M. A. Aldera, L. G. Magnus, R. P. M. Julie, B. L. Fanaroff, G. Fadana, Robert Lehmensiek, A. J. Otto, A. van der Byl, T. Mauch, T. J. van Balla, S. K. Sirothia, L. Sofeya, P. P. A. Kotzé, N. Mnyandu, M. S. de Villiers, T. Cheetham, J. S. Kenyon, R. Renil, J. M. Chalmers, Ian Heywood, A. M. Matthews, L. Richter, F. Kapp, S. Salie, A. R. Isaacson, I. P. T. Moeng, A. Peens-Hough, R. T. Lord, Dirk I. L. de Villiers, W. D. Cotton, V. A. Kasper, J. P. L. Main, Sharmila Goedhart, B. Hugo, L. P. Williams, C. Tasse, L. R. S. Brederode, A. Martens, M. G. Welz, S. J. Buchner, T. D. Abbott, Simon Perkins, M. C. Mphego, C.G. Van der Merwe, V. Van Tonder, C. T. G. Schollar, L. J. du Toit, Fernando Camilo, O. J. Mokone, A. J. Tiplady, T. G. H. Bennett, and B. Ngcebetsha

Subjects
Physics, 010504 meteorology & atmospheric sciences, Star formation, Image (category theory), Center (category theory), FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics, 01 natural sciences, Astrophysics - Astrophysics of Galaxies, Galaxy, Luminosity, law.invention, Radio telescope, Telescope, Space and Planetary Science, law, Astrophysics of Galaxies (astro-ph.GA), 0103 physical sciences, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Luminosity function (astronomy)
Abstract

We present the confusion-limited 1.28 GHz MeerKAT DEEP2 image covering one $\approx 68'$ FWHM primary beam area with $7.6''$ FWHM resolution and $0.55 \pm 0.01$ $\mu$Jy/beam rms noise. Its J2000 center position $\alpha=04^h 13^m 26.4^s$, $\delta=-80^\circ 00' 00''$ was selected to minimize artifacts caused by bright sources. We introduce the new 64-element MeerKAT array and describe commissioning observations to measure the primary beam attenuation pattern, estimate telescope pointing errors, and pinpoint $(u,v)$ coordinate errors caused by offsets in frequency or time. We constructed a 1.4 GHz differential source count by combining a power-law count fit to the DEEP2 confusion $P(D)$ distribution from $0.25$ to $10$ $\mu$Jy with counts of individual DEEP2 sources between $10$ $\mu$Jy and $2.5$ mJy. Most sources fainter than $S \sim 100$ $\mu$Jy are distant star-forming galaxies obeying the FIR/radio correlation, and sources stronger than $0.25$ $\mu$Jy account for $\sim93\%$ of the radio background produced by star-forming galaxies. For the first time, the DEEP2 source count has reached the depth needed to reveal the majority of the star formation history of the universe. A pure luminosity evolution of the 1.4 GHz local luminosity function consistent with the Madau & Dickinson (2014) model for the evolution of star-forming galaxies based on UV and infrared data underpredicts our 1.4 GHz source count in the range $-5 \lesssim \log[S(\mathrm{Jy})] \lesssim -4$., Comment: 20 pages, 18 figures. Accepted for publication in ApJ

Published
2019
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42. Evolution of the low-frequency pulse profile of PSR B2217+47

Author

J. Y. Donner, Michael Kramer, L. Bondonneau, Stefan Oslowski, J.-M. Grießmeier, M. Serylak, Aris Karastergiou, M. Pilia, M. Geyer, S. Sanidas, Jason W. T. Hessels, Daniele Michilli, Benjamin Stappers, Adam Deller, Joris P. W. Verbiest, Matthias Hoeft, Daniel R. Stinebring, L.N. Driessen, Patrick Weltevrede, B. Shaw, and High Energy Astrophys. & Astropart. Phys (API, FNWI)

Subjects
Physics, Scintillation, 010308 nuclear & particles physics, Astrophysics::High Energy Astrophysical Phenomena, Magnetosphere, Astronomy and Astrophysics, Astrophysics, LOFAR, 01 natural sciences, Pulse (physics), law.invention, Interstellar medium, Telescope, Pulsar, Space and Planetary Science, law, 0103 physical sciences, Precession, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics
Abstract

An evolution of the low-frequency pulse profile of PSR B2217+47 is observed during a six-year observing campaign with the LOFAR telescope at 150 MHz. The evolution is manifested as a new component in the profile trailing the main peak. The leading part of the profile, including a newly-observed weak component, is steady during the campaign. The transient component is not visible in simultaneous observations at 1500 MHz using the Lovell telescope, implying a chromatic effect. A variation in the dispersion measure of the source is detected in the same timespan. Precession of the pulsar and changes in the magnetosphere are investigated to explain the profile evolution. However, the listed properties favour a model based on turbulence in the interstellar medium (ISM). This interpretation is confirmed by a strong correlation between the intensity of the transient component and main peak in single pulses. Since PSR B2217+47 is the fourth brightest pulsar visible to LOFAR, we speculate that ISM-induced pulse profile evolution might be relatively common but subtle and that SKA-Low will detect many similar examples. In this scenario, similar studies of pulse profile evolution could be used in parallel with scintillation arcs to characterize the properties of the ISM.

Published
2018

43. MeerTime - the MeerKAT Key Science Program on Pulsar Timing

Author

V. M. Kaspi, Simon Johnston, Maura McLaughlin, Fernando Camilo, G. Theureau, Scott M. Ransom, Norbert Wex, Kavilan Moodley, W. van Straten, Jonathan Sievers, J. Brink, Benjamin Stappers, Aris Karastergiou, Michael Kramer, M. Burgay, M. Serylak, Michael Keith, Stefan Oslowski, N. D. R. Bhat, Matthew Bailes, Frederic A. Rasio, Ramesh Karuppusamy, Ewan Barr, Jason W. T. Hessels, D. J. Champion, A. Possenti, Ingrid H. Stairs, G. H. Jansseng, S. Buchner, Patrick Weltevrede, Andrew Jameson, 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), Laboratoire Univers et Théories (LUTH (UMR_8102)), 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)-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National d’Études Spatiales [Paris] (CNES), 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), 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), 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 ), Institut national des sciences de l'Univers ( INSU - CNRS ) -Observatoire de Paris-Université d'Orléans ( UO ) -Centre National de la Recherche Scientifique ( CNRS ), Laboratoire Univers et Théories ( LUTH ), and Institut national des sciences de l'Univers ( INSU - CNRS ) -Observatoire de Paris-Université Paris Diderot - Paris 7 ( UPD7 ) -Centre National de la Recherche Scientifique ( CNRS )

Subjects
[ PHYS.ASTR ] Physics [physics]/Astrophysics [astro-ph], Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Magnetar, 7. Clean energy, 01 natural sciences, Pulsar, Millisecond pulsar, 0103 physical sciences, [PHYS.PHYS.PHYS-INS-DET]Physics [physics]/Physics [physics]/Instrumentation and Detectors [physics.ins-det], [ PHYS.PHYS.PHYS-INS-DET ] Physics [physics]/Physics [physics]/Instrumentation and Detectors [physics.ins-det], Instrumentation and Methods for Astrophysics (astro-ph.IM), 010303 astronomy & astrophysics, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, Supermassive black hole, 010308 nuclear & particles physics, Gravitational wave, Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy, Neutron star, Globular cluster, Glitch (astronomy), Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract

The MeerKAT telescope represents an outstanding opportunity for radio pulsar timing science with its unique combination of a large collecting area and aperture efficiency (effective area $\sim$7500 m$^2$), system temperature ($T, 15 pages, MeerKAT Science: On the Pathway to the SKA, 25-27 May, 2016, Stellenbosch, South Africa, available at: https://pos.sissa.it/277/011/pdf

Published
2018

44. Revival of the Magnetar PSR J1622-4950:Observations with MeerKAT, Parkes, XMM-Newton, Swift, Chandra, and NuSTAR

Author

G C Du Toit, T. D. Abbott, A. J. T. Ramaila, P. S. Swart, P. Ntuli, G. de Bruin, Stephanie Smith, T. E. Monama, C. Stuart, Andrew Jameson, R. Spann, H. Kriel, N. Matthysen, J. Horrell, K. M. B. Asad, D. H. Botha, L. P. Williams, L. D. Mc Nally, R. T. Lord, A. Struthers, W. de Villiers, H. Niehaus, E. F. Bauermeister, John Sarkissian, B. Jordaan, R. Andreas, T. G. H. Bennett, J. P. Conradie, Riana Geschke, I. Wait, B. Ngcebetsha, A. van der Byl, Ben Stappers, A. Robyntjies, J. P. Jansen van Rensburg, N. Mabombo, D. H. Hoorn, A. Nzama, Bruce Merry, L. Sofeya, Sharmila Goedhart, L. R. S. Brederode, M. J. Hlakola, I. Rammala, O. Toruvanda, S. Rakoma, B. L. Fanaroff, A. Rust, A. Martens, M. G. Welz, Y. Padayachee, C. T. G. Schollar, S. J. Marais, B. Xaia, J. P. van Staden, F. Karels, T. Baloyi, B. de Swardt, I. Liebenberg, Vanessa A. Moss, A. L. Walker, C.G. Van der Merwe, W. S. New, E. C. Knox-Davies, R. Millenaar, P. Prozesky, L. J. du Toit, O. J. Mokone, K. Madisa, G. Sethosa, Griffin Foster, T. L. Grobler, Tom Alberts, S. S. Passmoor, F. Joubert, A. A. Patel, D. Koch, Ramesh Karuppusamy, L. Richter, Kshitij Thorat, O. Mahgoub, Jason Manley, C. Sharpe, M. J. Slabber, P. L. van der Merwe, S. Fataar, G. B. Taylor, M. Rasivhaga, P. Sunnylall, MacCalvin Kariseb, Gyula I. G. Józsa, A. R. Foley, N. Marais, M. A. Dikgale, J. P. Burger, C. Olyn, S. Paula, A. J. Otto, S. Ratcliffe, B. Pholoholo, R. Renil, T. Macdonald, Justin L. Jonas, R. van Rooyen, P. Scholz, Oleg Smirnov, B. H. Wallace, Fernando Camilo, A. Peens-Hough, S. Lamoor, F. Obies, L. Marais, T. J. Steyn, M. T. O. Ockards, O. Jacobs, C. Mjikelo, A. J. Tiplady, Roy Booth, D. Liebenberg, R. Strong, T. J. van Balla, P. C. van Niekerk, S. D. Matshawule, V. Van Tonder, C. de Waal, S. K. Sirothia, D. Rosekrans, R. M. Adam, L. Mafhungo, Matthew Bailes, G. Adams, P. P. A. Kotzé, D. M. Horn, S. Salie, M. S. de Villiers, Howard C. Reader, A. R. Isaacson, Dehann Fourie, B. Taljaard, C. de Villiers, A. F. Joubert, M. Serylak, T. Mauch, N. Sambu, Victoria M. Kaspi, C. C. Julius, N. Mnyandu, S. Seranyane, A. Krebs, Simon Johnston, N. Young, L. van den Heever, M. Manzini, R. van Wyk, M. Obrocka, N. Songqumase, T. W. Kusel, M. C. Mphego, J. A. Malan, I. P. T. Moeng, P. Malgas, K. J. Ngoasheng, B. M. Lunsky, L. C. Schwardt, M. Merryfield, W. van Straten, V. Thondikulam, B. Hugo, Nadeem Oozeer, Robert F. Archibald, P. Macfarlane, T. Cheetham, Aris Karastergiou, J. Conradie, D. Steyn, S. C. Gumede, S. Makhathini, S. W. P. Esterhuyse, N. Mkhabela, D. Booisen, R. P. M. Julie, Gianni Bernardi, L. Boyana, N. Kriek, Dirk I. L. de Villiers, T. Baxana, Cyril Tasse, M. Maree, Robert Lehmensiek, R. R. G. Gamatham, S. Zitha, D. E. Baker, K. Montshiwa, C. Magozore, Z. R. Ramudzuli, T. Gatsi, George Hobbs, S. J. Buchner, I. P. Theron, R. Siebrits, John Reynolds, A. Hokwana, F. Kapp, L. G. Magnus, V. A. Kasper, J. P. L. Main, J. van Aardt, David B. Davidson, ZAF, Unité Scientifique de la Station de Nançay (USN), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), Galaxies, Etoiles, Physique, Instrumentation (GEPI), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), 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), and PSL Research University (PSL)-PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Swift, individual (PSR J16224950) [pulsars], 010504 meteorology & atmospheric sciences, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Magnetosphere, Flux, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Ephemeris, Magnetar, 01 natural sciences, general [pulsars], stars: neutron, stars: magnetars, neutron [stars], Pulsar, pulsars: general, 0103 physical sciences, magnetars [stars], 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, computer.programming_language, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, Quiescent state, Astronomy and Astrophysics, Neutron star, pulsars: individual, Space and Planetary Science, Astrophysics - High Energy Astrophysical Phenomena, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], computer
Abstract

New radio (MeerKAT and Parkes) and X-ray (XMM-Newton, Swift, Chandra, and NuSTAR) observations of PSR J1622-4950 indicate that the magnetar, in a quiescent state since at least early 2015, reactivated between 2017 March 19 and April 5. The radio flux density, while variable, is approximately 100x larger than during its dormant state. The X-ray flux one month after reactivation was at least 800x larger than during quiescence, and has been decaying exponentially on a 111+/-19 day timescale. This high-flux state, together with a radio-derived rotational ephemeris, enabled for the first time the detection of X-ray pulsations for this magnetar. At 5%, the 0.3-6 keV pulsed fraction is comparable to the smallest observed for magnetars. The overall pulsar geometry inferred from polarized radio emission appears to be broadly consistent with that determined 6-8 years earlier. However, rotating vector model fits suggest that we are now seeing radio emission from a different location in the magnetosphere than previously. This indicates a novel way in which radio emission from magnetars can differ from that of ordinary pulsars. The torque on the neutron star is varying rapidly and unsteadily, as is common for magnetars following outburst, having changed by a factor of 7 within six months of reactivation., Comment: Published in ApJ (2018 April 5); 13 pages, 4 figures

Published
2018

45. Low-frequency pulse profile variation in PSR B2217+47: evidence for echoes from the interstellar medium

Author

J. Y. Donner, Benjamin Stappers, Daniel R. Stinebring, Patrick Weltevrede, B. Shaw, Daniele Michilli, Jason W. T. Hessels, J.-M. Grießmeier, Adam Deller, Maura Pilia, Joris P. W. Verbiest, Matthias Hoeft, Aris Karastergiou, Laura Driessen, M. Serylak, L. Bondonneau, M. Geyer, S. Sanidas, Stefan Oslowski, Michael Kramer, 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), 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), 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), 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
Electron density, [ PHYS.ASTR ] Physics [physics]/Astrophysics [astro-ph], Astrophysics::High Energy Astrophysical Phenomena, Population, FOS: Physical sciences, Astrophysics, Low frequency, 01 natural sciences, Pulsar, 0103 physical sciences, education, 010303 astronomy & astrophysics, ISM: general, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, education.field_of_study, pulsars: individual: PSR B2217+47, 010308 nuclear & particles physics, Astronomy and Astrophysics, LOFAR, Interstellar medium, radio continuum: ISM, 13. Climate action, Space and Planetary Science, Circular symmetry, Astrophysics - High Energy Astrophysical Phenomena, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Order of magnitude
Abstract

We have observed a complex and continuous change in the integrated pulse profile of PSR B2217+47, manifested as additional components trailing the main peak. These transient components are detected over 6 years at $150$ MHz using the LOw Frequency ARray (LOFAR), but they are not seen in contemporaneous Lovell observations at $1.5$ GHz. We argue that propagation effects in the ionized interstellar medium (IISM) are the most likely cause. The putative structures in the IISM causing the profile variation are roughly half-way between the pulsar and the Earth and have transverse radii $R \sim 30$ AU. We consider different models for the structures. Under the assumption of spherical symmetry, their implied average electron density is $\overline{n}_e \sim 100$ cm$^{-3}$. Since PSR B2217+47 is more than an order of magnitude brighter than the average pulsar population visible to LOFAR, similar profile variations would not have been identified in most pulsars, suggesting that subtle profile variations in low-frequency profiles might be more common than we have observed to date. Systematic studies of these variations at low frequencies can provide a new tool to investigate the proprieties of the IISM and the limits to the precision of pulsar timing., to be published in MNRAS

Published
2018

46. LOFAR 150-MHz observations of SS 433 and W 50

Author

Sera Markoff, John D. Swinbank, Gijs Molenaar, Rudy Wijnands, James Miller-Jones, Ralph A. M. J. Wijers, J. van Leeuwen, J.-M. Grießmeier, V. I. Kondratiev, Rob Fender, M. Pietka, Benjamin Stappers, S. A. Trushkin, Adam Stewart, J. W. Broderick, A. J. van der Horst, Rene P. Breton, Antonia Rowlinson, G. E. Anderson, Stephane Corbel, D. Carbone, Michael W. Wise, M. Serylak, Heino Falcke, P. Zarka, Jason W. T. Hessels, Martin Bell, Tim D. Staley, Jochen Eislöffel, Katherine M. Blundell, Casey J. Law, Laboratoire AIM, Université Paris Diderot - Paris 7 ( UPD7 ) -Centre d'Etudes de Saclay, Unité Scientifique de la Station de Nançay ( USN ), Institut national des sciences de l'Univers ( INSU - CNRS ) -Observatoire de Paris-Université d'Orléans ( UO ) -Centre National de la Recherche Scientifique ( CNRS ), 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 ), 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 Diderot - Paris 7 ( UPD7 ) -Centre National de la Recherche Scientifique ( CNRS ), Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), Unité Scientifique de la Station de Nançay (USN), Université d'Orléans (UO)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), PSL Research University (PSL)-PSL Research University (PSL)-Centre National d’Études Spatiales [Paris] (CNES), 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), High Energy Astrophys. & Astropart. Phys (API, FNWI), Faculty of Science, 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), Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), 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
Astronomy, Astrophysics::High Energy Astrophysical Phenomena, [ PHYS.ASTR ] Physics [physics]/Astrophysics [astro-ph], Flux, FOS: Physical sciences, stars: individual: SS 433, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, law.invention, Radio telescope, Telescope, law, 0103 physical sciences, Supernova remnant, 010303 astronomy & astrophysics, GeneralLiterature_REFERENCE(e.g.,dictionaries,encyclopedias,glossaries), Astrophysics::Galaxy Astrophysics, ISM: supernova remnants, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), ISM: individual objects: W50, 010308 nuclear & particles physics, Astronomy and Astrophysics, LOFAR, Galactic plane, Light curve, Astrophysics - Astrophysics of Galaxies, Stars, radio continuum: ISM, ISM: jets and outflows, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), Astrophysics - High Energy Astrophysical Phenomena, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], radio continuum: stars
Abstract

We present LOFAR high-band data over the frequency range 115-189 MHz for the X-ray binary SS 433, obtained in an observing campaign from 2013 February - 2014 May. Our results include a deep, wide-field map, allowing a detailed view of the surrounding supernova remnant W 50 at low radio frequencies, as well as a light curve for SS 433 determined from shorter monitoring runs. The complex morphology of W 50 is in excellent agreement with previously published higher-frequency maps; we find additional evidence for a spectral turnover in the eastern wing, potentially due to foreground free-free absorption. Furthermore, SS 433 is tentatively variable at 150 MHz, with both a debiased modulation index of 11 per cent and a $\chi^2$ probability of a flat light curve of $8.2 \times 10^{-3}$. By comparing the LOFAR flux densities with contemporaneous observations carried out at 4800 MHz with the RATAN-600 telescope, we suggest that an observed $\sim$0.5-1 Jy rise in the 150-MHz flux density may correspond to sustained flaring activity over a period of approximately six months at 4800 MHz. However, the increase is too large to be explained with a standard synchrotron bubble model. We also detect a wealth of structure along the nearby Galactic plane, including the most complete detection to date of the radio shell of the candidate supernova remnant G 38.7-1.4. This further demonstrates the potential of supernova remnant studies with the current generation of low-frequency radio telescopes., Comment: 19 pages, 8 figures, 4 tables, accepted for publication in MNRAS

Published
2018

47. 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

48. X-rays from the mode-switching PSR B0943+10

Author

M. Serylak, Sandro Mereghetti, Michela Rigoselli, G. A. E. Wright, Kevin Stovall, Jason W. T. Hessels, Andrea Tiengo, Paolo Esposito, Roberto Turolla, Stefan Oslowski, J. M. Griessmeier, W. Hermsen, Dipanjan Mitra, Andrea Possenti, Ben Stappers, Joanna M. Rankin, A. Horneffer, Lucien Kuiper, Unité Scientifique de la Station de Nançay (USN), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National d’Études Spatiales [Paris] (CNES), 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)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), PSL Research University (PSL)-PSL Research University (PSL)-Centre National d’Études Spatiales [Paris] (CNES), Mereghetti, S, Kuiper, L, Tiengo, A, Hessels, J, Hermsen, W, Stovall, K, Possenti, A, Rankin, J, Esposito, P, Turolla, R, Mitra, D, Wright, G, Stappers, B, Horneffer, A, Oslowski, S, Serylak, M, Griessmeier, J, Rigoselli, M, and High Energy Astrophys. & Astropart. Phys (API, FNWI)

Subjects
Physics, 010504 meteorology & atmospheric sciences, Astrophysics::High Energy Astrophysical Phenomena, Mode (statistics), Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy and Astrophysics, LOFAR, Astrophysics, Thermal emission, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Radio telescope, stars: neutron, Pulsar, Space and Planetary Science, pulsars: general, 0103 physical sciences, X-rays: individual (PSR B0943+10), Spectral analysis, Astrophysics - High Energy Astrophysical Phenomena, Polar cap, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, 0105 earth and related environmental sciences
Abstract

New simultaneous X-ray and radio observations of the archetypal mode-switching pulsar PSR B0943+10 have been carried out with XMM-Newton and the LOFAR, LWA and Arecibo radio telescopes in November 2014. They allowed us to better constrain the X-ray spectral and variability properties of this pulsar and to detect, for the first time, the X-ray pulsations also during the X-ray-fainter mode. The combined timing and spectral analysis indicates that unpulsed non-thermal emission, likely of magnetospheric origin, and pulsed thermal emission from a small polar cap are present during both radio modes and vary in a correlated way., Comment: 4 pages, 1 figure, 1 table - To appear in the proceedings of "IAUS 337: Pulsar Astrophysics - The Next 50 Years" eds: P. Weltevrede, B.B.P. Perera, L. Levin Preston & S. Sanidas

Published
2017

49. LOFAR imaging of Cygnus A - direct detection of a turnover in the hotspot radio spectra

Author

Aris Karastergiou, Michael W. Wise, Gianni Bernardi, Heino Falcke, L. Cerrigone, D. Engels, Michel Tagger, Simona Vegetti, Anna Nelles, R. Morganti, John D. Swinbank, Leith Godfrey, George Heald, I. van Bemmel, E. Juette, P. Maat, Sera Markoff, V. I. Kondratiev, Léon V. E. Koopmans, Huib Intema, Adam Deller, H. Munk, J. W. Broderick, Marcus Brüggen, R. Blaauw, J. Sluman, M. Iacobelli, R. J. van Weeren, Roberto Pizzo, Philip Best, A. J. van der Horst, D. McKay-Bukowski, Wilfred Frieswijk, M. Pandey-Pommier, Martin J. Hardcastle, M. Pietka, Aleksandar Shulevski, Rainer Beck, Satyendra Thoudam, M. Serylak, Matthias Steinmetz, Anna M. M. Scaife, Emanuela Orrú, Antonia Rowlinson, D. D. Mulcahy, Sarod Yatawatta, H. Paas, Adam Stewart, S. Duscha, I. M. Avruch, Frank Breitling, B. Ciardi, John McKean, H. J. A. Röttgering, R. C. Vermeulen, Oleg Smirnov, Olaf Wucknitz, W. Reich, Gottfried Mann, F. de Gasperin, P. Zarka, M. Kuniyoshi, D. Rafferty, Martin Bell, Richard Fallows, James M. Anderson, G. Kuper, Mark J. Bentum, M. A. Garrett, J.-M. Grießmeier, Matthias Hoeft, Christian Vocks, M. P. van Haarlem, M. C. Toribio, A. G. Polatidis, J. van Leeuwen, Annalisa Bonafede, Rebecca McFadden, Netherlands Institute for Radio Astronomy (ASTRON), SRON Netherlands Institute for Space Research (SRON), Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Amsterdam [Amsterdam] (UvA), University of Hertfordshire [Hatfield] (UH), Department of Astronomy and Astrophysics [PennState], Pennsylvania State University (Penn State), Penn State System-Penn State System, Department of Atmospheric and Planetary Sciences [Hampton] (APS), Hampton University, Kapteyn Astronomical Institute [Groningen], University of Groningen [Groningen], Université de Tours (UT), CSIRO Astronomy and Space Science, Commonwealth Scientific and Industrial Research Organisation [Canberra] (CSIRO), University of Southampton, 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, Jacobs University [Bremen], Leibniz-Institut für Astrophysik Potsdam (AIP), Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, Hamburger Sternwarte/Hamburg Observatory, Universität Hamburg (UHH), Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), Radboud University [Nijmegen], Institute of Mathematical and Physical Sciences, Leiden Observatory [Leiden], Universiteit Leiden, Unité Scientifique de la Station de Nançay (USN), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Joint Institute for VLBI in Europe (JIVE ERIC), Department of Pure Mathematics and Mathematical Statistics (DPMMS), Faculty of mathematics Centre for Mathematical Sciences [Cambridge] (CMS), University of Cambridge [UK] (CAM)-University of Cambridge [UK] (CAM), Ruhr-Universität Bochum [Bochum], Oxford Astrophysics, University of Oxford, Max-Planck-Institut für Radioastronomie (MPIFR), University of Oulu, University of Groningen, Groningen, Netherlands, 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), Australia Telescope National Facility (ATNF), School of Physics and Astronomy [Southampton], Department of Physics and Astronomy [South Africa], University of the Western Cape (UWC), 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], Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University-Smithsonian Institution, Argelander-Institut für Astronomie (AlfA), Rheinische Friedrich-Wilhelms-Universität Bonn, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), European Project: 320745,EC:FP7:ERC,ERC-2012-ADG_20120216,RADIOLIFE(2013), Astronomy, McKean, J.P., Godfrey, L.E.H., Vegetti, S., Wise, M.W., Morganti, R., Hardcastle, M.J., Rafferty, D., Anderson, J., Avruch, I.M., Beck, R., Bell, M.E., van Bemmel, I., Bentum, M.J., Bernardi, G., Best, P., Blaauw, R., Bonafede, A., Breitling, F., Broderick, J.W., Brüggen, M., Cerrigone, L., Ciardi, B., de Gasperin, F., Deller, A., Duscha, S., Engels, D., Falcke, H., Fallows, R.A., Frieswijk, W., Garrett, M.A., Grießmeier, J.M., van Haarlem, M.P., Heald, G., Hoeft, M., van der HorstA.J., null, Iacobelli, M., Interna, H., Juette, E., Karastergiou, A., Kondratiev, V.I., Koopmans, L.V.E., Kuniyoshi, M., Kuper, G., van Leeuwen, J., Maat, P., Mann, G., Markoff, S., McFadden, R., McKay-Bukowski, D., Mulcahy, D.D., Munk, H., Nelles, A., Orru, E., Paas, H., Pandey-Pommier, M., Pietka, M., Pizzo, R., Polatidis, A.G., Reich, W., Rottgering, H.J.A., Rowlinson, A., Scaife, A.M.M., Serylak, M., Shulevski, A., Sluman, J., Smirnov, O., Steinmetz, M., Stewart, A., Swinbank, J., Tagger, M., Thoudam, S., Toribio, M.C., Vermeulen, R., Vocks, C., van Weeren, R.J., Wucknitz, O., Yatawatta, S., Zarka, P., High Energy Astrophys. & Astropart. Phys (API, FNWI), 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), Radboud university [Nijmegen], Universiteit Leiden [Leiden], Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), 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), University of the Western Cape, Smithsonian Institution-Harvard University [Cambridge], ITA, GBR, FRA, DEU, NLD, Université de Tours, Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National d’Études Spatiales [Paris] (CNES), and Harvard University [Cambridge]-Smithsonian Institution

Subjects
Radio galaxy, Astronomy, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Radio continuum: galaxie, Spectral line, Radio spectrum, Radio continuum: galaxies, Galaxies: active: individual: Cygnus A, X-shaped radio galaxy, 0103 physical sciences, Cygnus A, 010303 astronomy & astrophysics, Physics, Spectral index, EWI-27659, 010308 nuclear & particles physics, LOBES, Astronomy and Astrophysics, LOFAR, Astronomy and Astrophysic, Astrophysics - Astrophysics of Galaxies, Galaxy, galaxies [radio continuum], GALAXIES, METIS-321690, RESOLUTION, Space and Planetary Science, HOT-SPOTS, GAS, [SDU]Sciences of the Universe [physics], Astrophysics of Galaxies (astro-ph.GA), ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, ARRAY, IR-103274
Abstract

The low-frequency radio spectra of the hotspots within powerful radio galaxies can provide valuable information about the physical processes operating at the site of the jet termination. These processes are responsible for the dissipation of jet kinetic energy, particle acceleration, and magnetic-field generation. Here we report new observations of the powerful radio galaxy Cygnus A using the Low Frequency Array (LOFAR) between 109 and 183 MHz, at an angular resolution of ~3.5 arcsec. The radio emission of the lobes is found to have a complex spectral index distribution, with a spectral steepening found towards the centre of the source. For the first time, a turnover in the radio spectrum of the two main hotspots of Cygnus A has been directly observed. By combining our LOFAR imaging with data from the Very Large Array at higher frequencies, we show that the very rapid turnover in the hotspot spectra cannot be explained by a low-energy cut-off in the electron energy distribution, as has been previously suggested. Thermal (free-free) absorption or synchrotron self absorption models are able to describe the low-frequency spectral shape of the hotspots, however, as with previous studies, we find that the implied model parameters are unlikely, and interpreting the spectra of the hotspots remains problematic., Comment: 9 pages, 3 figures, accepted for publication in MNRAS

Published
2016

50. Detection of decametre-wavelength pulsed radio emission of 40 known pulsars

Author

Ph. Zarka, I. Y. Vasylieva, O. M. Ulyanov, A. A. Konovalenko, Jean-Mathias Grießmeier, Ismaël Cognard, V. V. Zakharenko, V. Nikolaenko, M. Serylak, Institute of Radio Astronomy of NASU [Kharkiv] (IRA), National Academy of Sciences of Ukraine (NASU), Unité Scientifique de la Station de Nançay (USN), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National d’Études Spatiales [Paris] (CNES), 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), National Academy of Sciences of Ukraine and the Russian Foundation for Basic Research (Ukrainian–Russian Project 2012).NASUCNRSPICS program ‘Development of LF radioastronomy withultrahigh sensitivity and resolution’ (Grant 1.33.11)., ANR-05-BLAN-0018,RADIO-EXOPLA(2005), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), and 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)

Subjects
Physics, Scintillation, 010504 meteorology & atmospheric sciences, Scattering, Astrophysics::High Energy Astrophysical Phenomena, Astronomy, Astronomy and Astrophysics, Astrophysics, methods: data analysis, 01 natural sciences, Radio telescope, pulsars: individual: PSR B0031−07, Wavelength, Pulsar, [SDU]Sciences of the Universe [physics], Space and Planetary Science, pulsars: general, 0103 physical sciences, Dispersion (optics), Radio frequency, Ionosphere, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences
Abstract

International audience; The study of pulsars at the lowest radio frequencies observable from the ground (10-30 MHz) is complicated by strong interstellar (dispersion, scattering) and ionospheric (scintillation, refraction) propagation effects, as well as intense Galactic background noise and interference. However, it permits us to measure interstellar plasma parameters (the effects of which increase by a power of two to >4 times the wavelength), the spectrum and the pulse profile at low frequencies more accurately. Up to now, only ˜10 pulsars have been successfully detected at these frequencies. The recent upgrade of the receivers at the Ukrainian T-shaped Radio telescope, second modification (UTR-2) has increased its sensitivity and motivated a new search for pulsed radio emissions. In this work we carried out a survey of known pulsars with declination above -10°, period >0.1 s and dispersion measure (DM) < 30 pc cm-3, i.e. a sample of 74 sources. Our goal was either to detect pulsars not recorded before in the decametre range or to identify factors that prevent their detection. As a result, we have detected the radio emission of 40 pulsars, i.e. 55 per cent of the observed sample. For 30 of them, this was a first detection at these frequencies. Parameters of their average profiles have been calculated, including the intrinsic widening of the pulse (not due to interstellar scattering) with decreasing frequency. Furthermore, two pulsars beyond the selected DM (B0138+59 with DM ≈ 35 pc cm-3 and B0525+21 with DM ≈51 pc cm-3) were also detected. Our results indicate that there is still room to detect new transient and pulsed sources with low-frequency observations.

Published
2013

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