Luminous Blue Variables, cool hypergiants and some impostors in the H-R diagram

Abstract

Abstract. Current observations of the S Dor/LBVs and candidates and the implications for their important role in massive star evolution are reviewed. Recent observations of the cool hypergiants are altering our ideas about their evolutionary state, their atmospheres and winds, and the possible mechanisms for their asymmetric high mass loss episodes which may involve surface activity and magnetic fields. Recent results for IRC+I0420, peas and VYC:rvla are highlighted. S Dor/LBVs in eruption, and the cool hypergiants in their high mass loss phases with their optically thick winds are not what their apparent spectra and temperatures imply; they are then 'impostors' on the H-R diagram. The importance of the very most massive stars, like 'f/ Carinae and the 'supernovae impostors' are also discussed.