HST/FOS Spectroscopy of ETA Carinae: The Star Itself, and Ejecta Within 0.3 Arcsec
Walborn, Nolan R.; Weigelt, Gerd; Humphreys, Roberta M.; Davidson, Kris; Hajian, Arsen R.; Ebbets, Dennis; Rosa, Michael
United States, Germany
Abstract
Ground-based spectroscopy of η Car includes at least four components ABCD within a core region less than 0.4 across, and usually other material as well. Using the Hubble Space Telescope (HSTs) Faint Object Spectrograph (FOS), we have obtained separate data on component A and on B+C+D. Object A is found to be the central star; this is the fist time that the spectrum of the star η Car has been observed without a severe contamination by surrounding ejecta.The spectrum is that of a hot dense stellar wind with a mass-loss rate of the order of 10-3 solar mass/yr. A more detailed nonspherical analysis of the data has not yet been done. Objects BCD appear to be ejecta rather than companion stars, since their combined spectrum has many forbidden lines with no sign of any stellar spectrum different from that of A. Exitation mechanisms in BCD are of great interest and deserve more theoretical study.