Light variations of massive stars ( Cyg variables) *
XVI. The LMC supergiants R 85 (LBV) and R 110 (LBV) and the SMC supergiants R 42 and R 45
A.M. van Genderen 1,
** 2 and
M. de Groot 3
Received 19 February 1998 / Accepted 20 May 1998
Multi-colour photometry of four variable supergiants in the LMC and SMC, viz. R 85, R 110, R 42 and R 45, is searched for periods, studied and discussed. The suspected LBV R 85 is undoubtedly an active LBV, though not as spectacular as R 110. Their microvariations superimposed on the S Dor-activity are analyzed as well as those exhibited by R 42 and R 45. Often, a period search is difficult because of the very complicated micro-variability. We suggest that this is caused by an intricate multi-cyclic behaviour combined with stochastic processes. The length of the strongest cyclicity in the power spectrum of R 42 (128 d) is of the order of the rotation periods of BA-type supergiants.
In connection with our findings described in the present paper and the previous ones, we discuss various competing theoretical models on the instability of Cyg variables, including the LBVs.
Key words: stars: variables stars: supergiants stars: individual R 42 = HD 7099, R 45 = HD 7583, R 85 = HDE 269321, R 110 = HDE 269662
Send offprint requests to: A.M. van Genderen
© European Southern Observatory (ESO) 1998
Online publication: August 17, 1998