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DOI: 10.1051/aas:1998186
A&A Supplement series, Vol. 129, April II 1998, 289-311
Received March 11; accepted July 24, 1997
Long-term visual spectrophotometric behaviour
of Be stars
A. Moujtahid 
- J. Zorec 
- A.M. Hubert - A. Garcia - G. Burki 
Send offprint request: J. Zorec
Observatoire de Paris-Meudon, DASGAL, F-92195 Meudon Principal
Cedex, France
Institut d'Astrophysique de Paris, CNRS,
98
Bd.
Arago, F-75014 Paris, France
e-mail: zorec@iap.fr
Observatoire de
Genève, CH-1290 Sauverny, Switzerland
Abstract:
The long-term spectrophotometric variations of 49 Be stars are
studied using the U and V magnitudes of the UBV system, the total Balmer
discontinuity D and the visible gradient 
. BCD
spectrophotometric and photometric data in five different photometric systems,
obtained in most cases since 1950 and reduced to the BCD system, were used.
The (U,D), (V,D), (
) and (
) correlations
obtained differ from star to star and they can be single or double-valued. They
differ clearly for Be phases or Be-shell phases. Be stars with small 
showing the "spectrophotometric shell behaviour'': D > D*, were found. This
finding implies either that strongly flattened models of circumstellar envelopes
are in doubt for these stars, or that not all Be stars are rapid rotators.
Comparison of observed variations with those predicted for model Be stars with
spherical circumstellar envelopes of variable densities and dimensions implies
that spectrophotometric patterns of Be phases are due to circumstellar envelopes
in low opacity regimes, while those of spectrophotometric shell phases are due
to circumstellar envelopes in high opacity regimes. In a given star, the
envelope regions responsible for the observed variations of D and
in spectrophotometric shell phases seem to be smaller and denser than
those producing the observed variations of these parameters in
spectrophotometric Be phases. The high positive RV found in strong shell phases
might favor the formation of compact circumstellar layers near the star.
keywords: stars: variable -- stars: Be
SIMBAD ObjectsTables at the CDS
Copyright by the European Southern Observatory (ESO)
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