A study of the B and Be star population in the field of the LMC open cluster NGC 2004 with VLT-FLAMES

¹ GEPI, UMR8111 du CNRS, Observatoire de Paris-Meudon, 92195 Meudon Cedex, France e-mail: christophe.martayan@obspm.fr
² Universidad de Valencía, Instituto de Ciencia de los Materiales, PO Box 22085, 46071 Valencía, Spain
³ Royal Observatory of Belgium, 3 avenue Circulaire, 31180 Brussels, Belgium
⁴ Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 220B, 3001 Belgium
⁵ Observatoire de la Côte d'Azur, avenue Nicolas Copernic, 06130 Grasse, France
⁶ Institut d'Astrophysique de Paris (IAP), 98bis boulevard Arago, 75014 Paris, France

Received: 25 January 2005
Accepted: 21 August 2005

Abstract

Observations of hot stars belonging to the young cluster LMC-NGC 2004 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 (Hα and Hγ), [] and [] nebular lines. These lines are typical of regions. They could be associated with patchy nebulosities with a bi-modal distribution in radial velocity, with higher values (+335 km s^-1) preferentially seen inside the southern part of the known bubble LMC4 observed in at 21 cm.