Ma. Pogodin, RAPID LINE-PROFILE VARIABILITY OF H-ALPHA AND H-BETA IN THE A-TYPE SHELL STAR HD-163296, Astronomy and astrophysics, 282(1), 1994, pp. 141-150
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.