R Scuti: Close Alternating Pulsation Periods or Chaos in the RV Tau -- Type Star?

Abstract

Results of analysis of 60 010 data photometric observations from the AAVSO international database are presented, which span 120 years of monitoring. The periodogram analysis shows the best fit period of 70.74d, a half of typically published periods for smaller intervals. Contrary to expectation for deep/shallow minima, the changes between them are not so regular. There may be series of deep (or shallow) minima without alternations. There may be two acting periods of 138.5 days and 70.74, so the beat modulation may be expected. The dependence of the phases of deep minima argue for two alternating periods with a characteristic life-time of a mode of 30years. These phenomenological results better explain the variability than the model of chaos.