PHOTOMETRIC VARIABILITY OF B- AND A-TYPE SUPERGIANTS.

Photometric observations of 16 early-type (O9 to A3) supergiants have been obtained. All but two of the stars are variable, with a range of about 0.05 mag. The light curves are irregular, but characteristic time scales or 'quasi-periods' can be identified. The ratio of the quasi-period to the theoretical period (for pulsation in the fundamental radial mode) varies from 2-10 in the earliest-type supergiants to 0.2-2 in the later-type supergiants. The variability is most likely due to nonradial pulsation, at least in the O-B-type supergiants.