EVOLUTION OF GALACTIC FIELD Be STARS
Résumé
Galactic field Be stars were studied by taking into account the effects induced by the fast rotation on their fundamental parameters. Fractional ages $\tau/\tau_{\rm MS}$ ($\tau_{\rm MS}$ = time spent in the MS) against stellar mass reveal that: a) Be stars spread over the whole interval $0<\tau/\tau_{\rm MS}<1$; b) the Be phenomenon in massive stars ($M>12M_{\odot}$) is present at smaller age ratios than for less massive stars ($M<12M_{\odot}$); c) there is a lack of Be stars with $M<7M_{\odot}$ in the first half of the MS. Low mass fast rotators ($M<7M_{\odot}$), called Bn stars, could be "becoming" Be stars.
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