A study of the B and Be star population in the field of the LMC open cluster NGC2004 with VLT-FLAMES

Christophe Martayan (1) , Anne-Marie Hubert (1) , Michele Floquet (1) , Juan Fabregat (2) , Yves Fremat (3) , Coralie Neiner (1, 4) , Philippe Stee (5) , Jean Zorec (6)

1 GEPI - Galaxies, Etoiles, Physique, Instrumentation
2 Observatorio Astronomico de la Universidad de Valencia
3 ROB - Royal Observatory of Belgium = Observatoire Royal de Belgique
4 Instituut voor Sterrenkunde [Leuven]
5 OCA - Observatoire de la Côte d'Azur
6 IAP - Institut d'Astrophysique de Paris

Observations of hot stars belonging to the young cluster LMC-NGC2004 and its surrounding region have been obtained with the VLT-GIRAFFE facilities in MEDUSA mode. 25 Be stars were discovered; the proportion of Be stars compared to B-type stars is found to be of the same order in the LMC and in the Galaxy fields. 23 hot stars were discovered as spectroscopic binaries (SB1 and SB2), 5 of these are found to be eclipsing systems from the MACHO database, with periods of a few days. About 75% of the spectra in our sample are polluted by hydrogen (Halpha and Hgamma), [SII] and [NII] nebular lines. These lines are typical of HII regions. They could be associated with patchy nebulosities with a bi-modal distribution in radial velocity, with higher values (+335 kms^{-1}) preferentially seen inside the southern part of the known bubble LMC4 observed in HI at 21 cm.

Mots clés: Stars: early-type; Stars: emission-line; Be; Galaxies: Magellanic Clouds; Stars: binaries: spectroscopic; Stars: binaries: eclipsing; ISM: nebular lines and bands

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

Christophe Martayan, Anne-Marie Hubert, Michele Floquet, Juan Fabregat, Yves Fremat, et al.. A study of the B and Be star population in the field of the LMC open cluster NGC2004 with VLT-FLAMES. 2005. ⟨hal-00008693⟩