On outflowing viscous disc models for Be stars

Abstract

It is assumed that Be star discs are driven by viscosity. Emission from disc models is calculated and is confronted with continuum observations. It is found that the outflowing viscous disc models can reproduce the observed IR continuum emission. However, to exist as outflowing discs, either the discs are significantly acted upon by the stellar radiation field and/or there is significant cooling with radius in the disc. The energy generated via viscous dissipation is calculated and shown to play only a minor role in the energy balance of the disc. A scenario whereby a B star may change into a Be star (and vice versa) by generating (reaccreting) the disc is suggested.