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arXiv · 1211.3109

The Be/X-ray Binary Swift J1626.6-5156 as a Variable Cyclotron Line Source

Megan E. DeCesar·Patricia T. Boyd·Katja Pottschmidt·Jörn Wilms·Slawomir Suchy·M. Coleman Miller
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Abstract

Swift J1626.6-5156 is a Be/X-ray binary that was in outburst from December 2005 until November 2008. We have examined RXTE/PCA and HEXTE spectra of three long observations of this source taken early in its outburst, when the PCA 2-20 keV count rate was >70 counts/s/PCU, as well as several combined observations from different stages of the outburst. The spectra are best fit with an absorbed cutoff power law with a ~6.4 keV iron emission line and a Gaussian optical depth absorption line at ~10 keV. We present strong evidence that this absorption-like feature is a cyclotron resonance scattering feature, making Swift J1626.6-5156 a new candidate cyclotron line source. The redshifted energy of ~10 keV implies a magnetic field strength of ~8.6(1+z) x 10^11 G in the region of the accretion column close to the magnetic poles where the cyclotron line is produced. Analysis of phase averaged spectra spanning the duration of the outburst suggests a possible positive correlation between the fundamental cyclotron energy and source luminosity. Phase resolved spectroscopy from a long observation reveals a variable cyclotron line energy, with phase dependence similar to a variety of other pulsars, as well as the first harmonic of the fundamental cyclotron line.

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Megan E. DeCesar, Patricia T. Boyd, Katja Pottschmidt, Jörn Wilms, Slawomir Suchy, M. Coleman Miller. 2012-11-13. The Be/X-ray Binary Swift J1626.6-5156 as a Variable Cyclotron Line Source. https://doi.org/10.1088/0004-637x%2F762%2F1%2F61

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