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Session 25 - Stars in the Ultraviolet.
Display session, Tuesday, June 10
South Main Hall,
HST is used to study massive star populations in galaxies of the Local Group beyond the Magellanic Clouds (MC). The purpose is to compare massive star parameters in parent galaxies with different metallicities and star formation histories. The program provides useful data to test theories of stellar winds and stellar evolution, and information on the recent star formation history in Local Group galaxies.
Four WFPC2 fields in NGC6822 were observed in cycle 6, in U,B,V, far UV and H\alpha filters. Photometry results are shown for different locations in this galaxy.
Also, UV spectra with FOS and GHRS were obtained of five hot massive stars in NGC6822. We compare the observed UV line profiles with those of similar stars in other galaxies: the Milky Way, the Magellanic Clouds, M31 and M33 (from our previous HST programs), to test for metallicity effects. The wind terminal velocity is derived by modelling the UV line profiles. Analysis of the HST spectra and complementary ground based spectra also yields measurements of the mass loss rate and photospheric parameters (gravity, temperature, and rotation).
