OBSERVATIONS OF MASS LOSING SUPERGIANTS IN THE MAGELLANIC CLOUDS

we propose to obtain lowresolution fullscan sws01 spectra and pht03 25, 60 and 100 micron data for a sample of 15 supergiants (sgs) in the magellanic clouds (the clouds) which have a large infrared excess. iso is the only platform with the spectroscopic capability and sensitivity to observe stars over a wide wavelength range in galaxies other than our own. we will derive properties of the stellar and circumstellar environment of individual sgs in the clouds, in particular the mass loss rate (history), luminosity, intrinsic shape of the silicate 9.8 and 18 micron dust features and the effective temperature. this will be achieved by fitting the data with a radiative transfer model and followup groundbased observations. the results will be compared to that of similar observations of sgs in the galaxy obtained in the central program by tdejong_agbstars. this will provide information on the metallicity dependence of the mass loss rate, which is essentially not known at the moment, but is of key importance for the theory of dust driven stellar winds and for massive star evolution. with the luminosity, effective temperature and the mass loss rate of individual sgs known, the observations will be compared to, and constrain, evolutionary models of massive stars. this will lead to a better understanding of the postmain sequence evolution of massive stars in general, and the relative importance of blue > red and red > blue evolution, the presupernova progenitor type distribution, and the importance of the postrsg channel for wolfrayet star formation in particular. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]