THE BETA PICTORIS CIRCUMSTELLAR DISK .13. SURVEY OF THE VARIABLE CA-II LINES

We present here more than 200 Ca II K and H spectra of betaPictoris taken between Sept. 19, 1989 and Dec. 19, 1990. A lot of new variable features are observed, at small and high redshifts, together with a few blueshifted ones. The time scales for the variations are shown to be strongly dependent on the redshift of the variable lines. From this survey, we derive a rate of events of congruent-to 200 per year; we also show that in some cases the absorbing cloud covers less than 40 per cent of the stellar surface. The observed variations are analysed, and compared to those observed in the UV. These observations provide a unique opportunity to test our scenario of evaporating infalling bodies, in terms of velocity of variable lines, occurrence of variable events, small time scale variations and size of the absorbing cloud. We show that the observed velocity range for the variable components may be explained by this scenario, as well as the size of the absorbing clouds. New physical parameters are suggested to improve the present simulation but the main conclusions do not change. It also seems that the present statistics of events is not yet sufficient to definitely test the possible presence of a large perturbing body around betaPictoris, although the main characteristics of the present data are consistent with the predictions of such a model.