XMM-Newton observations of CXOU J010043.1-721134: the first deep look at the soft X-ray emission of a magnetar

Abstract

We present the analysis of six XMM-Newton observations of the Anomalous X-ray Pulsar CXOU J010043.1-721134, the magnetar candidate characterized by the lowest interstellar absorption. In contrast with all the other magnetar candidates, its X-ray spectrum cannot be fit by an absorbed power-law plus blackbody model. The sum of two (absorbed) blackbody components with kT1=0.30 keV and kT2=0.7 keV gives an acceptable fit, and the radii of the corresponding blackbody emission regions are R1=12.1 km and R2=1.7 km. The former value is consistent with emission from a large fraction of a neutron star surface and, given the well known distance of CXOU J010043.1-721134, that is located in the Small Magellanic Cloud, it provides the most constraining lower limit to a magnetar radius ever obtained. A more physical model, where resonant cyclotron scattering in the magnetar magnetosphere is taken into account, has also been successfully applied to this source.

5 pages (in emulate-apj style), 3 figures; accepted for publication in ApJ Letters

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• Discovery of a Pulsar-powered Bow Shock Nebula in the Small Magellanic Cloud Supernova Remnant DEMS5
• Central compact objects in Kes 79 and RCW 103 as "hidden" magnetars with crustal activity
• Deep Chandra Survey of the Small Magellanic Cloud. II. Timing Analysis of X-ray Pulsars
• X-Ray Observations of Magnetar SGR 0501+4516 from Outburst to Quiescence
• Long-term XMM-Newton view of magnetar CXOU J010043.1$-$721134: Comprehensive spectral and temporal results
• Discovery of a magnetar candidate X-ray pulsar in the Large Magellanic Cloud
• Pulsed, Polarized X-ray Emission from Neutron Star Surfaces: the Effects of Vacuum Birefringence in the Magnetosphere
• AstroSat observation of the magnetar SGR J1830$-$0645 during its first detected X-ray outburst
• Resonant Inverse Compton Scattering and Hard X-ray Emission in Magnetar Magnetospheres