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Evolution and appearance of Be stars in SMC clusters

Published online by Cambridge University Press:  18 January 2010

C. Martayan ,
D. Baade ,
Y. Frémat  and
J. Zorec
C. Martayan
Affiliation:
European Organisation for Astronomical Research in the Southern Hemisphere, Alonso de Cordova 3107, Vitacura, Casilla 19001, Santiago 19, Chile email: cmartaya@eso.org GEPI, Observatoire de Paris, CNRS, Université Paris Diderot, 5 place Jules Janssen, 92195 Meudon Cedex, France
D. Baade
Affiliation:
European Organisation for Astronomical Research in the Southern Hemisphere, Karl–Schwarzschild–Str. 2, 85748 Garching b. München, Germany
Y. Frémat
Affiliation:
Royal Observatory of Belgium, 3 avenue circulaire, 1180 Brussels, Belgium
J. Zorec
Affiliation:
Institut d'Astrophysique de Paris, UMR7095, CNRS, Université Marie & Pierre Curie, 98bis Boulevard Arago, 75014 Paris, France
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Abstract

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Star clusters are privileged laboratories for studying the evolution of massive stars (OB stars). One particularly interesting question concerns the phases during which the classical Be stars occur, which—unlike HAe/Be stars—are not pre-main-sequence objects, nor supergiants. Rather, they are extremely rapidly rotating B-type stars with a circumstellar decretion disk formed by episodic ejections of matter from the central star. To study the impact of mass, metallicity, and age on the Be phase, we observed Small Magellanic Cloud (SMC) open clusters with two different techniques: (i) with the ESO–WFI in slitless mode, which allowed us to find the brighter Be and other emission-line stars in 84 SMC open clusters, and (ii) with the VLT–FLAMES multifiber spectrograph to determine accurately the evolutionary phases of Be stars in the Be-star-rich SMC open cluster NGC 330. Based on a comparison to the Milky Way, a model of Be stellar evolution, appearance as a function of metallicity and mass, and spectral type is developed, involving the fractional critical rotation rate as a key parameter.

Keywords

stars: emission-lineBestars: fundamental parametersstars: statisticsstars: early-typestars: evolutionsurveysgalaxies: star clustersMagellanic Clouds
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 5 , Symposium S266: Star clusters: basic galactic building blocks throughout time and space , August 2009 , pp. 470 - 473
Copyright
Copyright © International Astronomical Union 2010

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