{
  "id": "2108.01749",
  "version": "v1",
  "published": "2021-08-03T21:04:35.000Z",
  "updated": "2021-08-03T21:04:35.000Z",
  "title": "Follow-up of 27 radio-quiet gamma-ray pulsars at 110-190 MHz using the international LOFAR station FR606",
  "authors": [
    "J. -M. Grießmeier",
    "D. A. Smith",
    "G. Theureau",
    "T. J. Johnson",
    "M. Kerr",
    "L. Bondonneau",
    "I. Cognard",
    "M. Serylak"
  ],
  "comment": "17 pages, 3 figures, 1 appendix. Accepted by A&A",
  "doi": "10.1051/0004-6361/202140841",
  "categories": [
    "astro-ph.HE"
  ],
  "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.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2021-08-03T21:04:35.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "international lofar station fr606",
      "radio-quiet gamma-ray pulsars",
      "low-frequency radio",
      "observation",
      "low radio frequencies"
    ],
    "tags": [
      "journal article"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 17,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}