New Results on Eta Carinae. Evidence for an Asymmetric, Inhomogeneous Wind

Extract

The very peculiar object Eta Car is one of the best laboratory for the study of those physical processes - such as mass loss, superionization, dust condensation, wind interaction with the i.s. medium - that presently are of great astrophysical interest, especially for the study of the most luminous stars. For its light history and high luminosity Eta Car may also be considered as the galactic counterpart of the Hubble-Sandage variables. Eta Car is one of the rare astrophysical objects with evidence of dust condensation from ejected stellar matter (Andriesse et al. 78) On the other side the star is also producing a strong, hard X-ray flux (Chlebowski et al. 1984), and the problem is whether there is any physical reason to have these two quite different processes in the same stellar environment. In any case rather extreme physical conditions are required which cannot be verified in a uniformly, spherically symmetric atmospheric enevelope. Andriesse et al. in fact suggested the presence of strong inhomogeneities, such as filaments, possibly related to the presence of a strong magnetic field. This may also explain the X-ray emission. In the following we shall present new optical and UV observations of Eta Car and its small nebula with the aim of clearfying the physical nature of its wind.