A PULSATING STAR INSIDE ETA-CARINAE .2. THE VARIABILITY OF THE PULSATION PERIOD

On the basis of photometric observations published since 1974, we pres ent new times of maximum light of the LBV eta Car, and discuss the var iation of the pulsation period. It is shown that-over more than two de cades-the pulsation period is stable at 58.(d)58 with a mean error of about half an hour. eta Car is the first LBV for which such a stable p ulsation period can be recognised. In addition, we present evidence fo r the possible presence of a secondary period which beats with the mai n period on a time scale of the order of 20 years.