NEBULAE AROUND LUMINOUS BLUE VARIABLES - A UNIFIED PICTURE

The study of the nebulae around luminous blue variables (LBVs) provide s clues to the mass-loss history of massive stars before and during th e LBV phase. In this paper we investigate the possibility that the LBV nebulae (LBVNs) are shaped by interacting winds. We compare the morph ologies of all known nebulae around LBVs, by compiling the results of our detailed coronagraphic imaging and spectroscopic studies of indivi dual LBVs and their nebulae together with other relevant information f rom the literature. Most LBVs exhibit axisymmetric morphologies, sugge sting that a single basic formation mechanism is involved. We propose that a model which consists of a stellar wind interacting with a preex isting density contrast (between the equatorial and polar directions) can explain most observed morphologies. There are several mechanisms w hich can produce the necessary density contrast, and at present it is difficult to determine definitively whether one or more of these mecha nisms have been operating in the different systems.