LINE FORMATION IN BE STAR ENVELOPES .2. DISK OSCILLATIONS

We present numerical model calculations for an especially interesting class of H alpha emission line profiles from Be star disks, those with asymmetric shape and long-term variability (so-called class 2 profile s). As an underlying, model for the disk we investigate the hypothesis of Okazaki (1991) that these profiles are caused by a distortion of a quasi-Keplerian disk. The distortion has the form of a one-armed glob al disk oscillation (density and velocity wave).The radiation transfer in the disk is calculated with an improved version of the spatially i mplicit 3D radiative transfer code of Hummel (1994). The resulting set s of H alpha emission line profiles reproduce well the observed struct ures of fully-resolved class 2 H alpha emission lines, like double pea ks and winebottle-type shoulders. For high inclinations, shell-type pr ofiles result. It is shown that the full variety of observed profile s hapes is caused by the interaction of kinematical and non-coherent sca ttering broadening. While this result has already been found by Hummel (1994) for the symmetric (class 1) H alpha profiles, it is proven her e for the second major profile class as well. The comparison between o bserved and theoretical emission shows that the model of global disk o scillations is in full agreement with the observed shapes and the cycl ic long-term variability of class 2 profiles.