Journal Article

Discovery of millisecond pulsars in radio searches of southern <i>Fermi</i> Large Area Telescope sources

M. J. Keith, S. Johnston, P. S. Ray, E. C. Ferrara, P. M. Saz Parkinson, Ö. Çelik, A. Belfiore, D. Donato, C. C. Cheung, A. A. Abdo, F. Camilo, P. C. C. Freire, L. Guillemot, A. K. Harding, M. Kramer, P. F. Michelson, S. M. Ransom, R. W. Romani, D. A. Smith, D. J. Thompson, P. Weltevrede and K. S. Wood

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 414, issue 2, pages 1292-1300
Published in print June 2011 | ISSN: 0035-8711
Published online June 2011 | e-ISSN: 1365-2966 | DOI:
Discovery of millisecond pulsars in radio searches of southern Fermi Large Area Telescope sources

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Using the Parkes Radio Telescope, we have carried out deep observations of 11 unassociated gamma-ray sources. Periodicity searches of these data have discovered two millisecond pulsars, PSR J1103−5403 (1FGL J1103.9−5355) and PSR J2241−5236 (1FGL J2241.9−5236), and a long-period pulsar, PSR J1604−44 (1FGL J1604.7−4443). In addition, we searched for but did not detect any radio pulsations from six gamma-ray pulsars discovered by the Fermi satellite to a level of ∼0.04 mJy (for pulsars with a 10 per cent duty cycle).

The timing of the millisecond pulsar PSR J1103−5403 has shown that its position is 9 arcmin from the centroid of the gamma-ray source. Since these observations were carried out, independent evidence has shown that 1FGL J1103.9−5355 is associated with the flat spectrum radio source PKS 1101−536. It appears certain that the pulsar is not associated with the gamma-ray source, despite the seemingly low probability of a chance detection of a radio millisecond pulsar. We consider that PSR J1604−44 is a chance discovery of a weak, long-period pulsar and is unlikely to be associated with 1FGL J1604.7−4443. PSR J2241−5236 has a spin period of 2.2 ms and orbits a very low mass companion with a 3.5-h orbital period. The relatively high flux density and low dispersion measure of PSR J2241−5236 make it an excellent candidate for high precision timing experiments. The gamma rays of 1FGL J2241.9−5236 have a spectrum that is well modelled by a power law with an exponential cut-off, and phase binning with the radio ephemeris results in a multipeaked gamma-ray pulse profile. Observations with Chandra have identified a coincident X-ray source within 0.1 arcsec of the position of the pulsar obtained by radio timing.

Keywords: pulsars: general; pulsars: individual: J2241−5236

Journal Article.  6393 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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