Footprints in the wind of Vela X-1 traced with MAXI
Abstract
The stellar wind around a compact object in luminous wind-accreting high-mass X-ray binaries is expected to be strongly ionized with the X-rays coming from the compact object. The stellar wind of hot stars is mostly driven by light absorption in lines of heavier elements, and X-ray photo-ionization significantly reduces the radiative force within the so-called Strömgren region, leading to wind stagnation around the compact object. In close binaries like Vela X-1 this effect might alter the wind structure throughout the system. Using the spectral data from the Monitor of All-sky X-ray Image (MAXI), we studied the observed dependence of the photoelectric absorption as a function of the orbital phase in Vela X-1 and found that it is inconsistent with expectations for a spherically symmetric smooth wind. Taking into account previous investigations, we developed a simple model for wind structure with a stream-like photoionization wake region of slower and denser wind trailing the neutron star, which is responsible for the observed absorption curve.
The movie associated to Fig. 3 is available in electronic form at http://www.aanda.org- Publication:
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Astronomy and Astrophysics
- Pub Date:
- June 2013
- DOI:
- 10.1051/0004-6361/201321305
- arXiv:
- arXiv:1304.5965
- Bibcode:
- 2013A&A...554A..37D
- Keywords:
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- binaries: eclipsing;
- X-rays: binaries;
- pulsars: individual: Vela X-1;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- 5 pages, 3 figures, accepted in A&