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Astron. Astrophys. 361, 231-239 (2000)

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High-resolution spectroscopy of the SMC eclipsing binary HD 5980: the HeII [FORMULA]4686 emission line *

J. Breysacher 1 and P. François 2,3

1 European Southern Observatory (ESO), Karl-Schwarzschild-Strasse 2, 85748 Garching bei München, Germany (jbreysac@eso.org)
2 European Southern Observatory (ESO), Alonso de Cordova 3107, Vitacura, Casilla 19001, Santiago 19, Chile (fpatrick@eso.org)
3 Observatoire de Paris-Meudon, DASGAL, 5 place Jules Janssen, 92195 Meudon, France

Received 21 February 2000 / Accepted 7 June 2000

Abstract

During 25 nights distributed between September 1996 and September 1997, a programme of intensive spectroscopy of the SMC WR binary HD 5980 was conducted, providing a series of 116 high-resolution (R = 60 000) profiles of the HeII [FORMULA]4686 emission line. These observations were complemented with 9 additional spectra obtained: 5 in October-November 1998 and 4 in January 1999, with a resolving power of R = 48 000. This observational material has allowed to investigate, as a function of the orbital phase, the variations of the line equivalent width, of the full line width at half-maximum, and of the line radial velocity, over many different orbits. The discovery, on one night, of a profile oscillation at the red side of the emission, on a timescale of [FORMULA] 7 hours, is reported. Though revealing a rather complex phase-dependent behaviour of the HeII [FORMULA]4686 line, the analysis of the present data still favours the hypothesis that in HD 5980 this highly variable emission feature does not characterize a genuine WR star, but arises instead in a wind-wind collision shock zone.

Key words: line profiles – techniques: spectroscopic – stars: binaries: eclipsing – stars: individual: HD 5980 – galaxies: Magellanic Clouds

* Based on observations carried out at ESO, La Silla, Chile

Send offprint requests to: J. Breysacher

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© European Southern Observatory (ESO) 2000

Online publication: September 5, 2000
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