Reference : The spectrum of the very massive binary system WR20a (WN6ha+WN6ha): Fundamental param...
Scientific journals : Article
Physical, chemical, mathematical & earth Sciences : Earth sciences & physical geography
http://hdl.handle.net/2268/10157
The spectrum of the very massive binary system WR20a (WN6ha+WN6ha): Fundamental parameters and wind interactions
English
Rauw, Grégor mailto [Université de Liège - ULg > Département d'astrophys., géophysique et océanographie (AGO) > Groupe d'astrophysique des hautes énergies (GAPHE) >]
Crowther, P. A. [> > > >]
De Becker, Michaël mailto [Université de Liège - ULg > Département d'astrophys., géophysique et océanographie (AGO) > Groupe d'astrophysique des hautes énergies (GAPHE) >]
Gosset, Eric mailto [Université de Liège - ULg > Département d'astrophys., géophysique et océanographie (AGO) > Groupe d'astrophysique des hautes énergies (GAPHE) >]
Nazé, Yaël mailto [Université de Liège - ULg > Département d'astrophys., géophysique et océanographie (AGO) > Groupe d'astrophysique des hautes énergies (GAPHE) >]
Sana, H. [> > > >]
van der Hucht, K. A. [> > > >]
Vreux, Jean-Marie mailto [Université de Liège - ULg > Département d'astrophysique]
Williams, P. M. [> > > >]
Mar-2005
Astronomy and Astrophysics
E D P Sciences
432
3
985-998
Yes (verified by ORBi)
International
0004-6361
Les Ulis Cedex A
[en] stars : binaries : spectroscopic ; stars : early-type ; stars : fundamental parameters ; stars : individual : WR20a ; stars : Wolf-Rayet
[en] We analyse the optical spectrum of the very massive binary system WR20a (WN6ha + WN6ha). The most prominent emission lines, Halpha and He II lambda4686, display strong phase-locked profile variability. From the variations of their equivalent widths and from a tomographic analysis, we find that part of the line emission probably arises in a wind interaction region between the stars. Our analysis of the optical spectrum of WR20a indicates a reddening of A(nu) similar or equal to 6.0 mag and a distance of similar to 7.9 kpc, suggesting that the star actually belongs to the open cluster Westerlund 2. The location of the system at similar to 1.1 pc from the cluster core could indicate that WR20a was gently ejected from the core via dynamical interactions. Using a non-LTE model atmosphere code, we derive the fundamental parameters of each component: T-eff = 43 000 +/- 2000 K, log L-bol/ L-. similar or equal to 6.0, (M) over dot = 8.5 x 10(-6) M-. yr(-1) (assuming a clumped wind with a volume filling factor f = 0.1). Nitrogen is enhanced in the atmospheres of the components of WR20a, while carbon is definitely depleted. Finally, the position of the binary components in the Hertzsprung-Russell diagram suggests that they are core hydrogen burning stars in a pre-LBV stage and their current atmospheric chemical composition probably results from rotational mixing that might be enhanced in a close binary compared to a single star of same age.
Researchers ; Professionals
http://hdl.handle.net/2268/10157
10.1051/0004-6361:20042136
http://adsabs.harvard.edu/abs/2005A%26A...432..985R

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