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Astron. Astrophys. 318, 443-460 (1997)


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Critical study of the frequency of Be stars taking into account their outstanding characteristics

J. Zorec 1 and D. Briot 2

1 Institut d'Astrophysique de Paris, C.N.R.S. - [FORMULA], bd. Arago, F-75014 Paris, France (zorec@iap.fr)
2 Observatoire de Paris - 61, av. de l'Observatoire, F-75014 Paris, France

Received 31 October 1995 / Accepted 13 June 1996

Abstract

A new determination of the frequency of Be stars among B stars is presented for each spectral type and luminosity class. The most outstanding characteristics of Be stars are taken into account: errors in spectral type determinations; difference of absolute magnitudes of B and Be stars due to the presence of a circumstellar envelope; volume differences of magnitude-limited samples of various spectral types; changes in magnitude, spectral type and luminosity class due to the fast rotation of Be stars; change in spectral type during constant mass evolution from the main sequence to luminosity class III. The mean frequency over the whole sample is at least 17 % and a frequency as high as 34 % is obtained for Be stars of spectral type B1e. The frequency is the highest for B1e whereas previous results found a maximum for B2e stars. The same frequency is obtained for each luminosity class. This result, as well as the high value of this frequency, imply that Be stars can hardly represent a given stage in the evolutionary track of every B star. This suggest that the Be character could be interpreted as existing since the formation of the star.

Key words: stars: emission-line; Be – stars: statistics; circumstellar matter – stars: evolution

Send offprint requests to: J. Zorec

© European Southern Observatory (ESO) 1997

Online publication: July 8, 1998

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