On the behaviour of B and Be stars at low metallicity.

Christophe Martayan (1, 2) , Yves Fremat (1) , Anne-Marie Hubert (2) , Michele Floquet (2) , Coralie Neiner (2) , Jean Zorec (3) , Dietrich Baade (4) , Juan Gutiérrez-Soto (2, 5) , Juan Fabregat (5) , Malek Mekkas (2)

1 ROB - Royal Observatory of Belgium = Observatoire Royal de Belgique
2 GEPI - Galaxies, Etoiles, Physique, Instrumentation
3 IAP - Institut d'Astrophysique de Paris
4 ESO - European Southern Observatory
5 Observatorio Astronomico de Valencia

We present new results obtained with the VLT GIRAFFE for a large sample of B and Be stars belonging to the Magellanic Clouds, i.e. at low metallicity. First, we show the effects of the metallicity of the environment on their rotation (linear, angular, and at the ZAMS). Second, we present the analysis of the effects of metallicity and evolution on the appearance of Be stars. We also new present results about the proportions of Be stars to B stars. Third, by cross-correlation with large photometric surveys such as MACHO and OGLE, we report on the detection for the first time of short-term multi-periodicity in 9 Be stars in the Small Magellanic Cloud, which can be interpreted in terms of pulsations.

Mots clés: Emission line stars: Be; hot stars; Galaxies: Magellanic Clouds; metallicity; pulsations; VLT

Domaines: Cosmologie et astrophysique extra-galactique [astro-ph.CO]; Astrophysique [astro-ph]

Christophe Martayan, Yves Fremat, Anne-Marie Hubert, Michele Floquet, Coralie Neiner, et al.. On the behaviour of B and Be stars at low metallicity.. 2007. ⟨hal-00172962v2⟩