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.
Categories: astro-ph