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Evidence of a cyclotron feature in the spectrum of the anomalous X-ray pulsar 1RXS J170849-400910

Nanda Rea·Gian Luca Israel·Luigi Stella·Tim Oosterbroek·Sandro Mereghetti·Lorella Angelini·Sergio Campana·Stefano Covino
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Abstract

We report the results of a long observation of the anomalous X-ray pulsar 1RXS J170849-400910 obtained with the BeppoSAX satellite in August 2001. The best-fit phase-averaged spectrum was an absorbed power law plus blackbody model, with photon index Gamma~2.4 and a blackbody temperature of kT_bb~0.4 keV. We confirm the presence of significant spectral variations with the rotational phase of the pulsar. In the spectrum corresponding to the rising part of the pulse we found an absorption-like feature at ~8.1 keV (a significance of 4 sigma), most likely due to cyclotron resonant scattering. The centroid energy converts to a magnetic field of 9x10^11 G and 1.6x10^15 G in the case of electrons and protons, respectively. If confirmed, this would be the first detection of a cyclotron feature in the spectrum of an anomalous X-ray pulsar.

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Nanda Rea, Gian Luca Israel, Luigi Stella, Tim Oosterbroek, Sandro Mereghetti, Lorella Angelini, Sergio Campana, Stefano Covino. 2003-02-24. Evidence of a cyclotron feature in the spectrum of the anomalous X-ray pulsar 1RXS J170849-400910. https://doi.org/10.1086/374585

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