The circumstellar envelopes of Be stars: viscous disc dynamics

Abstract

We have constructed models of axisymmetric, circumstellar envelopes for Be star discs by successfully combining two numerical codes: a non-local thermodynamic equilibrium (non-LTE) radiative transfer code which calculates the level populations and disc temperature distribution self-consistently, and a hydrodynamical code. The output of one code is used as input to the other code, and hence evolving density and thermal structures may be examined. The temperatures, disc density and velocity distribution are used to investigate the outflowing viscous disc model for Be stars. We find that these simulations place constraints on the power-law density decrease in the disc with increasing distance from the star. We find that the power-law index for the line-forming region of the disc lies between 3 and 3.5 with a small dispersion.