DYNAMICS OF THE ENVELOPES OF BE STARS IN THE EQUATORIAL PLANE

We have investigated the dynamics in the equatorial plane of models for the envelopes of Be stars first by inverting the equation of motion to solve for the unknown force, F(x)(r), in addition to those arising from gravitation, rotation, and gas pressure gradient, required to produce a radial component of velocity having an assumed functional form. We then determined F(x)(r) for both a beta velocity and a power-law velocity dependence, and for each investigated the consequences for F(x)(r) of the assumptions of angular momentum conservation, Keplerian rotation, and the variation of kinetic temperature with r. We also used the simple models of Waters and coworkers deduced from analysis of the continuous energy distributions of six Be stars. All our results indicate that F(x)(r) has a similar characteristic shape. Between the surface of the star and a turning point of order 10-100 stellar radii, F(x)(r) decreases with increasing r, but less rapidly than does gravity. Beyond the turning point, F(x)(r) increases with r at least initially; however, it may again decrease with further increases in r. We discuss several physical effects, one or more of which may be responsible for this common form of F(x)(r).