Mass Loss and Non-Radial Pulsations in Be Stars

Abstract

The interpretation of infra-red observations of Be stars made with IRAS is discussed. This shows that a slow stellar wind is leaving the star forming an equatorial disc. The mass loss rate is 50 to 100 times greater than that deduced from the ultraviolet observations, which show a fast rapidly accelerating wind coming presumably from the star outside the equatorial region. The large mass loss and slow velocities imply a mechanism for the stellar wind in the equatorial regions which is different from the radiatively driven wind.

The observations of non-radial pulsations in Be stars which have their maximum amplitude confined to the equatorial regions suggest a possible origin of the mass loss forming the disc. A theory of mass loss driven by sound waves is given. It is assumed that the sound wave are generated by the non-radial pulsations. This mechanism does give a slow stellar wind, but further work is necessary to find out whether the theory can explain the Be star observations.