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Physical Properties of Circumstellar Envelopes in Be Stars Derived from their Long-term Spectrophotometric Variations

Published online by Cambridge University Press:  12 April 2016

A. Moujtahid
Affiliation:
Observatoire de Paris-Meudon, DASGAL/UMR 8633 du CNRS, F-92195 Meudon Principal Cedex, France
J. Zorec
Affiliation:
Institut d’Astrophysique de Paris, CNRS, 98bisbd. Arago, F-75014 Paris, France
A.M. Hubert
Affiliation:
Observatoire de Paris-Meudon, DASGAL/UMR 8633 du CNRS, F-92195 Meudon Principal Cedex, France

Abstract

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The long-term visible spectrophotometric variations depicted by the following parameters: V the apparent visual magnitude; Φrb the gradient of the observed Paschen energy distribution and D the total Balmer discontinuity (BD) of 49 Be stars in different spectrophotometric phases (SPh-E: spectrophotometric phase where the second component of the BD is in emission; SPh-A: spectrophotometric phase where the second component of the BD is in absorption) were translated into CE physical parameters. These parameters are: R/R* the mean extent of the CE zone that produces the visible energy distribution; Tenv its mean temperature; τ the continuum opacity at λ0.56μm. The results obtained show that the triplet of parameters (V, Φrb, D) do not depend on the (R/R*, Tenv, τ) set of parameters in the same way if Be stars are in a SPh-E or in a SPh-A phase. Independently of the spectrophotometric phase, Tenv always decreases as a linear function of (R/R*)−1. In SPh-E it is (R/R*,)−1 ≤ 0.7, and in SPh-A it is (R/R*)−1 ≥ 0.7. All SPh behaviours can be summarized by the relation ∂Tenv/∂(R*/R) = ∂Tenv/∂τ × ∂τ/(R*/R) ≥ 0, which describes different spectrophotometric behaviours in both SPh-E and SPh-A phases.

Type
6. Disks
Copyright
Copyright © Astronomical Society of the Pacific 2000

References

Moujtahid, A., Zorec, J., Hubert, A.M. 1998, A&AS 129, 289 Google Scholar
Moujtahid, A., Zorec, J., Hubert, A.M. 1999, A&A 349, 151 Google Scholar