Variable mass-flux in Be stars

Abstract

The available observational data concerning the variability of Be stars is briefly reviewed, and some different hypotheses concerning the origin of Be variability are examined. It is shown that variability in Be stars is not restricted to short time scales. In fact, long term variations (such as 'E/C' variations of the intensity of the emission components of H I lines relative to neighboring continua) may be greater in amplitude than short term variations. It is recommended that future calculations of Be rotational velocities (v sin i) take into account the uncertainty of short-term line profile variations. Observations of variability in the ultraviolet and X-ray regions are discussed within the framework of the mass-flux model of Doazan and Thomas (1982), in which mass-flux and nonradiative energy are assumed to be independent parameters.