Variability and mass loss in the extreme supergiant zet01 Sco.

Abstract

It is found that the photometric variability can be characterized by a unique relationship between the half-period and the amplitude in the V band. This kind of variability differs from that characterizing the best known pulsating stars. One explanation, advanced tentatively, is that p and g modes are simultaneously excited. What is considered a more attractive hypothesis is that Zeta(1) Sco is vibrationally unstable because of the importance of the radiation pressure with respect to the gas pressure in such a very massive star. The shape of the UV resonance lines varies strongly with time. Besides the global variation of the P Cygni profiles, narrow shifted absorption features are observable, the intensity of which is also variable. These absorption components become stronger with larger photometric variations. Since, however, they are stable in velocity during at least seven days, it is concluded that they cannot follow the same velocity law as the material producing the global P Cygni profiles.