GAMMA-DORADUS - EVIDENCE FOR A NEW CLASS OF PULSATING STAR

We present further photometric observations of the peculiar F-type dwa rf gamma Doradus. The two periodicities discovered previously are stil l present and phase-locked. In addition, there is marginal evidence fo r a third period not present in previous data. The hypothesis that the star is singly periodic with a double-wave light curve is shown to be untenable. The light variations are modelled by two starspots in diff erential rotation. The large size of the spots and the high stability of their periods count against this hypothesis. We conclude that the m ost plausible cause of the light and line-profile variations is low-de gree g-mode non-radial pulsation. This star is the best example of wha t appears to be a new class of pulsating F-type variable. The light va riations cannot be fully accounted for by two periods; the nature of t he aperiodic component is briefly discussed.