Interpretation of variable line profiles of Deneb (A2Ia)

The results of high-dispersion spectroscopic observations during the period from 1962 to 1974 of Deneb are presented. It is shown that (1) equivalent widths of metallic lines simultaneously change in the same sense, (2) the central depths of metallic lines and Hγ, and the depth of the apparent minimum of Hα deepen with the increase of equivalent widths of metallic lines, (3) the wing of Hγ shows no appreciable variation, and (4) Hα always exhibits a P Cygni-type profile, whose intensity varies with time. We try to check how much the variations in profile are accounted for by the change of microturbulence field. It is shown that the central depths of metallic lines cannot be reproduced by the model atmosphere computations as the equivalent widths become large. Therefore, we conclude that within the limits of plane-parallel geometry, the variations in profile are difficult to explain in terms of the change of microturbulence field so long as LTE is assumed. A brief discussion is presented for the need to seek an agency which predicts the drop of surface temperature by about 900K. (auth.)