A photoelectric study of three southern [delta] Scuti stars

Abstract

Differential photometric observations of the three [delta] Scuti stars AI, WZ and XX Sculptoris were obtained on ten nights during October 1978. None of these three stars had been extensively observed before, and the detailed nature of their variability was therefore unknown. The data obtained were then carefully examined for periodic behavior. For AI Scl, no strict periodicities were found, although a tendency to pulsate with a period of 134 minutes was found. For WZ Scl, periods of 94.69 and 138.16 minutes were found and for XX Scl, periods of 70.413 and 73.944 minutes were found. Because the periods for XX Scl lead to a beat period of almost one day, the entire light curve could not be observed and there remains some ambiguity about the correct values of the periods. For all three stars, the periods and colours were interpreted using theoretical studies of [delta] Scuti stars. Based on this study, it is suggested that all three stars are pulsating in overtone pulsation, and not the fundamental mode. For XX Scl the two periods may be caused by a degenerate non-radial mode splitting into two distinct modes, due to rotation.