Pi Aquarii: A pulsating Be star

Following the discovery by Ringuelet and Machado of large periodic radial-velocity variations in π Aqr, photometric observations of the star have been obtained. It is found that the star has undergone small but significant secular changes in brightness and color since observations made 11 years earlier, and that it also shows instabilities of the order of several hundreths of a magnitude on a time scale of hours or less. Several possible explanations, such as rotation, presence of a binary companion, varying emission lines, and pulsation, are considered. Of these, only pulsation seems plausible