10 research outputs found
Chandra Observations of WR147 Reveal a Double X-ray Source
We report the first results from deep X-ray observations of the Wolf-Rayet
binary system WR147 with the Chandra HETG. Analysis of the zeroth order data
reveals that WR147 is a double X-ray source. The northern counterpart is likely
associated with the colliding wind region, while the southern component is
certainly identified with the WN star in this massive binary. The latter is the
source of high energy X-rays (including the Fe K_alpha complex at 6.67 keV)
whose production mechanism is yet unclear. For the first time, X-rays are
observed directly from a WR star in a binary system.Comment: 15 pages, 3 figures, To Appear in The Astrophysical Journal Letter
Chandra HETG Observations of the Colliding Stellar Wind System WR 147
We present an extended analysis of deep Chandra HETG observations of the
WR+OB binary system WR 147 that was resolved into a double X-ray source (Zhekov
& Park, 2010, ApJ, 709, L119). Our analysis of the profiles of strong emission
lines shows that their centroids are blue-shifted in the spectrum of the
northern X-ray source. We find no suppressed forbidden line in the He-like
triplets which indicates that the X-ray emitting region is not located near
enough to the stars in the binary system to be significantly affected by their
UV radiation. The most likely physical picture that emerges from the entire set
of HETG data suggests that the northern X-ray source can be associated with the
colliding stellar wind region in the wide WR+OB binary system, while the X-rays
of its southern counterpart, the WN8 star, are result from stellar wind
shocking onto a close companion (a hypothesized third star in the system).Comment: 22 pages, 6 figures, 2 Tables; accepted for publication in The
Astrophysical Journa
Modelling X-ray variability in the structured atmospheres of hot stars
We describe X-ray production in the atmospheres of hot, early- type stars in the framework of a "stochastic shock model". The extended envelope of a star is assumed to possess numerous X- ray emitting "hot" zones that are produced by shocks and embedded in the ambient "cold" medium in dynamical equilibrium. It is shown that the apparent lack of X-ray variability on short (similar to hours) timescales do not contradict a shock model for X-ray production. The character of the X-ray variability is found to depend on the frequency with which hot zones are generated, the cool wind opacity to X-rays, and the wind ow parameters, such as mass loss rate and terminal speed