http://arxiv.org/abs/1310.7705
We report an XMM-Newton serendipitous discovery of an 11.56 s X-ray pulsar coinciding with 3XMM J185246.6+003317 and located south of the supernova remnant (SNR) Kes 79. The spin-down rate of 3XMM J185246.6+003317 is ~3.2e-11 s s^{-1}, which, together with the long period, indicates a high dipolar surface magnetic field of 6.2e14 G, a characteristic age of 5.7 kyr, and a spin-down luminosity of 8.2e32 erg s^{-1}. The X-ray spectrum of the source is best-fitted with a resonant Compton scattering model, and can be also adequately described by a blackbody model. The observations covering a 7-month span from 2008 to 2009 show variations in the spectral properties of the source, with the luminosity decreasing from 2.8e34 erg s^{-1} to 4.7e33 erg s^{-1} (at an assumed distance of 7.1 kpc), along with a decrease of the blackbody temperature from kT~0.8 keV to ~0.6 keV. The X-ray luminosity of the source is higher than its spin-down luminosity, ruling out rotation as a source of power. The combined timing and spectral properties of 3XMM J185246.6+003317, together with its lack of detection in archival X-ray data prior to the 2008 XMM-Newton observation, point to this source being a newly discovered transient magnetar. Its period is the longest among currently known transient magnetars. Its foreground absorption and characteristic age are similar to those of the nearby SNR Kes79, which suggests a possible connection between them. If so, 3XMM J185246.6+003317 would have a very high projected velocity (2.6e3 km s^{-1}).
Date added: Wed, 30 Oct 13
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