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P92 |
April
2004
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To be published in:
Astronomy & Astrophysics Letters
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WR 20a: a massive cornerstone binary system comprising two extreme early-type stars +
G. Rauw1,*,
M. De Becker1,
Y. Nazé1,**,
P.A. Crowther2,
E. Gosset1,*,
H. Sana1,**,
K.A. van der Hucht3,4,
J.-M. Vreux1 and
P.M. Williams5
1 Institut d'Astrophysique et de Géophysique - Université de Liège, Allée du 6 Août, Bât B5c, B-4000 Liège (Sart Tilman), Belgium
2 Department of Physics & Astronomy, University of Sheffield, Hicks Building, Hounsfield Rd., Sheffield, S3 7RH, UK
3 SRON National Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands
4 Astronomical Institute Anton Pannekoek, University of Amsterdam, Kruislaan 403, 1098 SJ Amsterdam, The Netherlands
5 Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh, EH9 3HJ, UK
* Research Associate FNRS, Belgium
** Research Fellow FNRS, Belgium
+ Based on observations collected at the European Southern Observatory (La Silla, Chile).
We analyse spectroscopic observations of WR 20a revealing that this star is
a massive early-type binary system with a most probable orbital period of
3.675 days. Our spectra indicate that both components are most likely of
WN6ha or O3If*/WN6ha spectral type. The orbital solution for a
period of 3.675 days yields extremely large minimum masses of 70.7 ±
4.0 and 68.8 ±3.8 M
for the two stars. These properties make WR 20a a cornerstone system for
the study of massive star evolution.
binaries: spectroscopic -- stars: early-type --
stars: fundamental parameters -- stars: individual: WR 20a
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