Issue |
A&A
Volume 654, October 2021
|
|
---|---|---|
Article Number | A43 | |
Number of page(s) | 14 | |
Section | Galactic structure, stellar clusters and populations | |
DOI | https://doi.org/10.1051/0004-6361/202140841 | |
Published online | 08 October 2021 |
Follow-up of 27 radio-quiet gamma-ray pulsars at 110–190 MHz using the international LOFAR station FR606
1
LPC2E – Université d’Orléans/CNRS, France
e-mail: jean-mathias.griessmeier@cnrs-orleans.fr
2
Station de Radioastronomie de Nançay, Observatoire de Paris – CNRS/INSU, USR 704 – Univ. Orléans, OSUC, Route de Souesmes, 18330 Nançay, France
3
Centre d’Études Nucléaires de Bordeaux Gradignan, IN2P3/CNRS, Université Bordeaux, 33175 Gradignan, France
4
Laboratoire d’Astrophysique de Bordeaux, Université Bordeaux, B18N, Allée Geoffroy Saint-Hilaire, 33615 Pessac, France
5
Laboratoire Univers et Théories LUTh, Observatoire de Paris, CNRS/INSU, Université Paris Diderot, 5 Place Jules Janssen, 92190 Meudon, France
6
College of Science, George Mason University, Fairfax, VA 22030, USA
7
Resident at Naval Research Laboratory, Washington, DC 20375, USA
8
Space Science Division, Naval Research Laboratory, Washington, DC 20375-5352, USA
9
LESIA, Observatoire de Paris, CNRS, PSL, SU/UP/UO, 92195 Meudon, France
10
South African Radio Astronomy Observatory, 2 Fir Street, Black River Park, Observatory 7925, South Africa
11
Department of Physics and Astronomy, University of the Western Cape, Bellville, Cape Town 7535, South Africa
Received:
19
March
2021
Accepted:
14
July
2021
Context. The Fermi Large Area Telescope has detected over 260 gamma-ray pulsars. About one quarter of these are labeled as radio-quiet, that is they either have radio flux densities < 30 μJy at 1400 MHz, or they are not detected at all in the radio domain. In the population of nonrecycled gamma-ray pulsars, the fraction of radio-quiet pulsars is higher, about one half.
Aims. 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.
Methods. 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 band (110−190 MHz), with an average observing time of 13 h per target. Part of the data had to be discarded due to radio frequency interference. On average, we kept 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.
Results. 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.
Conclusions. 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.
Key words: pulsars: general / telescopes / ISM: general
© J.-M. Grießmeier et al. 2021
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.