ASCA spectroscopy of the hard X-ray emission from the colliding wind interaction in γ<sup><nobr>2</nobr></sup> Velorum期刊界 All Journals 搜尽天下杂志传播学术成果专业期刊搜索期刊信息化学术搜索

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ASCA spectroscopy of the hard X-ray emission from the colliding wind interaction in γ² Velorum

Authors:	G Rauw † I R Stevens J M Pittard M F Corcoran

Institution:	Institut d'Astrophysique &Géophysique, Universitéde Liège, 5, Avenue de Cointe, B-4000 Liège, Belgium;School of Physics &Astronomy, University of Birmingham, Edgbaston, Birmingham B15 2TT;Department of Physics &Astronomy, University of Leeds, Woodhouse Lane, Leeds LS2 9JT;USRA/LHEA, Goddard Space Flight Center, Greenbelt, MD 20771, USA

Abstract:	We discuss an ASCA observation of the eccentric WC8+O7.5 III binary γ ² Velorum near apastron. The X-ray spectrum is compared with two previous observations obtained when the system was near periastron. All three spectra display a hard-emission component that undergoes strong variability over the orbital cycle. The properties of the hard X-ray emission of γ ² Vel are constrained by taking into account the contribution from contaminating soft X-ray sources in the vicinity of γ ² Vel. We find that the observed variations are in qualitative agreement with the predictions of colliding wind models. We investigate for the first time the effect of uncertainties in the chemical composition of the X-ray emitting plasma on our understanding of the high-energy properties of the wind interaction region. Our results indicate that these uncertainties significantly affect the derived shock temperature and absorption column, but play a smaller role in determining the intrinsic X-ray luminosity of the colliding wind zone. We further find that the intrinsic luminosity from the hard X-ray component in γ ² Vel does not follow the 1/ D distance relation expected from simple models of adiabatic shocks.

Keywords:	binaries: general stars: individual: γ² Vel stars: mass-loss stars: Wolf–Rayet X-rays: stars

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