Publication details

X-Ray Photoionized Bubble in the Wind of Vela X-1 Pulsar Supergiant Companion



Year of publication 2012
Type Article in Periodical
Magazine / Source Astrophysical Journal
MU Faculty or unit

Faculty of Science

Field Astronomy and astrophysics
Keywords hydrodynamics; radiative transfer; stars: early-type; stars: mass-loss; stars: winds; outflows
Description Vela X-1 is the archetype of high-mass X-ray binaries (HMXBs), 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 HMXBs. We unveil 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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