Wind Variability of LBV Stars

Abstract

General properties of Luminous Blue Variables (LBV) have been reviewed by Lamers(1987). The LBV’s are all close to the Humphreys-Davidson luminosity upper limit. The semi periods of the photometric microvariations with ΔV ∼ 0.1^m are about twice as large as for normal supergiants of the same L and T_eff, and 4–20 times larger than the fundamental mode for radial pulsations. So, it is likely due to nonradial pulsations. During shell ejections, which accompanied by moderate photometric variations of ΔV ∼ 1^m, L-_bol remains constant. This fact has been explained by the quasiperiodic variations of T _eff and the radius of pseudo-photosphere (Lamer 1986). LBV’s are less stable than normal supergiants so that any internal instability has more effect on their envelopes. The nature of these instabilities remains unknown. We have found some interesting peculiarities which can throw light to this problem.