Effects of metallicity, star-formation conditions, and evolution in B and Be stars. II: Small Magellanic Cloud, field of NGC 330.Reportar como inadecuado




Effects of metallicity, star-formation conditions, and evolution in B and Be stars. II: Small Magellanic Cloud, field of NGC 330. - Descarga este documento en PDF. Documentación en PDF para descargar gratis. Disponible también para leer online.

1 GEPI - Galaxies, Etoiles, Physique, Instrumentation 2 Royal Observatory of Belgium Brussels 3 IAP - Institut d-Astrophysique de Paris

Abstract : We search for effects of metallicity on B and Be stars in the Small and Large Magellanic Clouds SMC and LMC and in the Milky Way MW. We extend our previous analysis of B and Be stars populations in the LMC to the SMC. The rotational velocities of massive stars and the evolutionary status of Be stars are examined with respect to their environments. Spectroscopic observations of hot stars belonging to the young cluster SMC-NGC 330 and its surrounding region have been obtained with the VLT-GIRAFFE facilities in MEDUSA mode. We determine fundamental parameters for B and Be stars with the GIRFIT code, taking into account the effect of fast rotation, and the age of observed clusters. We compare the mean vsini obtained by spectral type- and mass-selection for field and cluster B and Be stars in the SMC with the one in the LMC and MW. We find that i B and Be stars rotate faster in the SMC than in the LMC, and in the LMC than in the MW; ii at a given metallicity, Be stars begin their main sequence life with a higher initial rotational velocity than B stars. Consequently, only a fraction of B stars that reach the ZAMS with a sufficiently high initial rotational velocity can become Be stars; iii the distributions of initial rotational velocities at the ZAMS for Be stars in the SMC, LMC and MW are mass- and metallicity-dependent; iv the angular velocities of B and Be stars are higher in the SMC than in the LMC and MW; v in the SMC and LMC, massive Be stars appear in the second part of the main sequence, contrary to massive Be stars in the MW.

Keywords : Stars: early-type Stars: emission-line Be Galaxies: Magellanic Clouds Stars: fundamental parameters Stars: evolution Stars: rotation





Autor: Christophe Martayan - Yves Frémat - Anne-Marie Hubert - Michele Floquet - Jean Zorec - Coralie Neiner -

Fuente: https://hal.archives-ouvertes.fr/



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