Tuning in to Bright Sources

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Science  28 Jan 2011:
Vol. 331, Issue 6016, pp. 378-379
DOI: 10.1126/science.331.6016.378-c

The Fermi space telescope has revealed thousands of new sources of gamma-ray emission; however, the nature of hundreds of them remains a mystery. To check whether some of the unidentified sources could be pulsars, Ransom et al. searched for radio pulsations in 25 sources in the Fermi Large Area Telescope Bright Source List—a catalog of the brightest sources detected in the early months of the Fermi mission. These 25 sources were selected to be nonvariable and not associated with known pulsars, black holes at the centers of galaxies, or x-ray sources that had previously been searched for radio pulsations. Radio observations with the Green Bank Telescope revealed three pulsars with millisecond periods, all of which are in binary systems where a neutron star and a companion star orbit one another about their common center of mass. The new pulsars have properties consistent with those of typical radio millisecond pulsars. Their detection suggests that most, if not all, radio millisecond pulsars produce gamma rays, and that their radio and gamma-ray beams are comparable in size. It is thus possible that millisecond pulsars contribute to the diffuse isotropic gamma-ray background.

Astrophys. J. 727, L16 (2011).

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