Footprints in the wind of Vela X-1 traced with MAXI
Abstract
The stellar wind around the 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 Stroemgren 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 Monitor of All-sky X-ray Image (MAXI), we study the observed dependence of the photoelectric absorption as function of orbital phase in Vela X-1, and find that it is inconsistent with expectations for a spherically-symmetric smooth wind. Taking into account previous investigations we develop a simple model for wind structure with a stream-like photoionization wake region of slower and denser wind trailing the neutron star responsible for the observed absorption curve.
Cite
@article{arxiv.1304.5965,
title = {Footprints in the wind of Vela X-1 traced with MAXI},
author = {V. Doroshenko and A. Santangelo and S. Nakahira and T. Mihara and M. Sugizaki and M. Matsuoka and M. Nakajima and K. Makishima},
journal= {arXiv preprint arXiv:1304.5965},
year = {2015}
}
Comments
5 pages, 3 figures, accepted in A&A