RAPID LINE-PROFILE VARIABILITY OF H-ALPHA AND H-BETA IN THE A-TYPE SHELL STAR HD-163296

The results of the H alpha and H beta line profile investigation of an AO-shell star HD 163296 are presented. 47 high-resolution CCD spectra (35 for H alpha and 12 for H beta) were obtained on July 15-20, 1991 and on July 24-27, 1992. A considerable profile variability is found o n time scales from one hour to a few days. The main properties of the night-to-night variations are strong change in shape of the entire lin e profile with the exception of the primary PCyg-absorption which rema ins relatively constant both in strength and in position. Two types of extremely rapid variations (tau similar to hours) are discovered: (a) positional shift of sharp spectral bumps, and (b) monotonous flux var iations of different parts of a profile during a night. A qualitative explanation in the framework of the model for an envelope containing a n active non-stable region formed by an equatorially concentrated stel lar wind and an external cool shell is proposed for the observed varia bility. Some reasons for the extremely rapid profile changes are consi dered.