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Abstract: Star clusters are privileged laboratories for studying the evolution ofmassive stars OB stars. One particularly interesting question concerns thephases, during which the classical Be stars occur, which unlike HAe-Be stars,are not pre-main sequence objects, nor supergiants. Rather, they are extremelyrapidly rotating B-type stars with a circumstellar decretion disk formed byepisodic ejections of matter from the central star. To study the impact ofmass, metallicity, and age on the Be phase, we observed SMC open clusters withtwo different techniques: 1 with the ESO-WFI in its slitless mode, whichallowed us to find the brighter Be and other emission-line stars in 84 SMC openclusters 2 with the VLT-FLAMES multi-fiber spectrograph in order to determineaccurately the evolutionary phases of Be stars in the Be-star rich SMC opencluster NGC 330. Based on a comparison to the Milky Way, a model of Be stellarevolution - appearance as a function of metallicity and mass - spectral type isdeveloped, involving the fractional critical rotation rate as a key parameter.



Autor: Christophe Martayan ESO-Chile, GEPI, Dietrich Baade ESO-HQ, Yves Fremat, Jean Zorec IAP

Fuente: https://arxiv.org/







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