Long-term spectral and timing properties of the soft gamma-ray repeater SGR1833-0832 and detection of extended X-ray emission around the radio pulsar PSRB1830-08

Abstract

SGR1833-0832 was discovered on 2010 March 19, thanks to the Swift detection of a short hard X-ray burst and follow-up X-ray observations. Since then, it was repeatedly observed with Swift, Rossi X-ray Timing Explorer and XMM-Newton. Using these data, which span about 225d, we studied the long-term spectral and timing characteristics of SGR1833-0832. We found evidence for diffuse emission surrounding SGR1833-0832, which is most likely a halo produced by the scattering of the point-source X-ray radiation by dust along the line of sight, and we show that the source X-ray spectrum is well described by an absorbed blackbody, with temperature kT~ 1.2keV and absorbing column NH= (10.4 ± 0.2) × 1022cm-2, while different or more complex models are disfavoured. The source persistent X-ray emission remained fairly constant at ~3.7 × 10-12 erg cm-2s-1 for the first ~20d after the onset of the bursting episode, then it faded by a factor of ~40 in the subsequent ~140d, following a power-law trend with index α≃-0.5. We obtained a phase-coherent timing solution with the longest baseline (~225d) to date for this source which, besides period P= 7.5654084(4)s and period derivative ss-1, includes higher order period derivatives. We also report on our search of the counterpart to the soft gamma-ray repeater (SGR) at radio frequencies using the Australia Telescope Compact Array and the Parkes Radio Telescope. No evidence for radio emission was found, down to flux densities of 0.9mJy (at 1.5 GHz) and 0.09mJy (at 1.4 GHz) for the continuum and pulsed emissions, respectively, consistently with other observations at different epochs. Finally, the analysis of the field of PSRB1830-08 (J1833-0827), which was serendipitously imaged by the XMM-Newton observations, led to the discovery of the X-ray pulsar wind nebula generated by this 85-ms radio pulsar. We discuss its possible association with the unidentified TeV source HESSJ1834-087. © 2011 The Authors Monthly Notices of the Royal Astronomical Society © 2011 RAS.