The Pulse-Phase–dependent Spectrum of the Anomalous X-Ray Pulsar 1RXS J170849−400910 (original) (raw)

We report on the results of a 50 ks BeppoSAX observation of 1RXS J170849−400910, one of the five (plus a candidate) known anomalous X-ray pulsars. The BeppoSAX data are consistent with a power-law plus blackbody spectral decomposition, making 1RXS J170849−400910 the fourth source of this class for which such a spectral decomposition was found. The inferred power-law slope and blackbody temperature are Γ ∼2.6 and kT BB ∼0.46 keV, respectively. We found significant energy-dependence of the pulse profile, a remarkable feature for an AXP. By using the power-law plus blackbody decomposition we detected a significant variation in at least one spectral parameter, the power-law photon index, as a function of the pulse phase. This is the first significant detection of spectral parameter variation in an AXP. The implications of these results are briefly discussed.