Reference : Phase-resolved XMM-Newton observations of the massive WR+O binary WR 22
Scientific journals : Article
Physical, chemical, mathematical & earth Sciences : Space science, astronomy & astrophysics
http://hdl.handle.net/2268/35226
Phase-resolved XMM-Newton observations of the massive WR+O binary WR 22
English
Gosset, Eric mailto [Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Groupe d'astrophysique des hautes énergies (GAPHE) >]
Nazé, Yaël mailto [Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Astrophysique observationnelle (sol et espace) >]
Sana, H. [European Southern Observatory, Alonso de Cordova 3107, Vitacura, Casilla 19001, 19 Santiago de Chile, Chile]
Rauw, Grégor mailto [Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Groupe d'astrophysique des hautes énergies (GAPHE) - Sciences spatiales >]
Vreux, Jean-Marie mailto [Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > > ]
1-Dec-2009
Astronomy and Astrophysics
508
805-821
Yes (verified by ORBi)
International
0004-6361
[en] stars: Wolf-Rayet ; stars: individual: WR 22 ; binaries: general ; X-rays: stars ; X-rays: binaries
[en] Aims. To better understand the phenomenon of colliding winds in massive binary stars, we study the X-ray lightcurve of a WR+O system of the Carina region, a system well known for the high mass of its primary.<BR /> Methods: Phase-resolved X-ray observations of the massive WR+O binary system WR 22 were performed with the XMM-Newton facility. We observed the object at seven different phases from near apastron to near periastron.<BR /> Results: The X-ray spectrum can be represented by a two-component, optically thin, thermal plasma model with a first one at a typical temperature of 0.6 keV and a second hotter one in the range 2.0-4.5 keV. The hot component is indicative of a colliding wind phenomenon, but its flux is remarkably constant with time despite the high eccentricity of the orbit. Although surprising at first, this actually does not contradict the results of the hydrodynamical simulations of the wind collision that we performed. When the system goes from apastron to periastron, the soft part of the X-ray flux is progressively lowered by an increasing intervening absorbing column. This behaviour can be interpreted in terms of an X-ray emitting plasma located near the O star, but not fully intrinsic to it, and accompanying the star when it dives into the wind of the WR component. A model is presented that interprets most of the observational constraints. This model suggests that the mass-loss rate of dot{M}[SUB]WR[/SUB] 1.6 à 10[SUP]-5[/SUP] {M}[SUB]ȯ[/SUB] yr[SUP]-1[/SUP] assumed for the WR could still be slightly too high, whereas it is already lower than other published values. From the comparison of the observed and the expected absorptions at phases near periastron, we deduce that the hard X-ray emitting collision zone should at least have a typical size of 50-60 R[SUB]ȯ[/SUB], but that the size for the soft X-ray emitting region could reach 244 R[SUB]ȯ[/SUB] if the assumed mass-loss rate is correct. We also present an upper limit to the X-ray luminosity of the WR component that further questions the existence of intrinsic X-ray emission from single WN stars.<BR /> Based on observations with XMM-Newton, an ESA Science Mission with instruments and contributions directly funded by ESA Member States and the USA (NASA). Research Associate FNRS (Belgium). Postdoctoral Researcher FNRS (Belgium).
http://hdl.handle.net/2268/35226
10.1051/0004-6361/20077981
http://adsabs.harvard.edu/abs/2009A%26A...508..805G

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