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arXiv · 1208.1827

X-ray photoionized bubble in the wind of Vela X-1 pulsar supergiant companion

Jiri Krticka·Jiri Kubat·Jan Skalicky
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Abstract

Vela X-1 is the archetype of high-mass X-ray binaries, composed of a neutron star and a massive B supergiant. The supergiant is a source of a strong radiatively-driven stellar wind. The neutron star sweeps up this wind, and creates a huge amount of X-rays as a result of energy release during the process of wind accretion. Here we provide detailed NLTE models of the Vela X-1 envelope. We study how the X-rays photoionize the wind and destroy the ions responsible for the wind acceleration. The resulting decrease of the radiative force explains the observed reduction of the wind terminal velocity in a direction to the neutron star. The X-rays create a distinct photoionized region around the neutron star filled with a stagnating flow. The existence of such photoionized bubbles is a general property of high-mass X-ray binaries. We unveiled a new principle governing these complex objects, according to which there is an upper limit to the X-ray luminosity the compact star can have without suspending the wind due to inefficient line driving

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Jiri Krticka, Jiri Kubat, Jan Skalicky. 2012-08-09. X-ray photoionized bubble in the wind of Vela X-1 pulsar supergiant companion. https://doi.org/10.1088/0004-637x/757/2/162

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