Recherche systématique d'etoiles binaires parmi les étoiles Wolf-Rayet de sous-type spectral WNE dans les Nuages de Magellan; Recherche systématique d'etoiles binaires parmi les étoiles Wolf-Rayet de sous-type spectral WNE dans les Nuages de Magellan; Systematic search for binary stars among Wolf-Rayet stars of spectral subtype WNE in Magellanic Clouds;
Abstract
We have made an intensive spectroscopic campaign to search for binaries via periodic radial-velocity (RV) variations among Wolf-Rayet (WR) stars in the Magellanic Clouds (MCs). We observed 61 nitrogen-rich WNE stars in the LMC and all the WN stars in the SMC. We have also retrieved time-dependent photometric data in the public domain from the OGLE and MACHO projects, as well as X-ray data from the ROSAT and Chandra satellites, to provide additional constraints on the binary character. For each of our sample stars, we discuss its observational properties: RV variations, (periodic) photometric variability, X-ray luminosity, spectral classification, abundance of hydrogen, runaway status and line-profile variations (LPVs). For the binaries we discuss additional properties, like wind-wind collision (WWC) effects, and the orbital parameters. For this large sample, we discuss the global properties of the WNE population, which is expected to be the most sensitive to binary evolution with regard to the influence of metallicity. For a few binary stars, we are able to discuss their evolutionary status in regard of the massive-star binary models. To emphasize the relevance of the binary frequency test for the stellar evolution of massive stars in the MCs, we review their observational properties and provide new and meaningful evolutionary classes, which reconcile observational and theoretical definitions. Finally, we draw an overall evolutionary scheme for massive-star evolution, with respect to the three main ingredients of stellar evolution: mass, metallicity and rotation.
- Publication:
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Ph.D. Thesis
- Pub Date:
- December 2003
- Bibcode:
- 2003PhDT.........6F
- Keywords:
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- French text;
- Physics: Astronomy and Astrophysics