F. Kemper (University of Virginia), R. Szczerba (NCAC Torun, Poland), S. D. Van Dyk (IPAC/CalTech), M. Meixner (STScI)
We present Spitzer-IRS spectroscopy of mass-losing post-main-sequence stars in the Large Magellanic Cloud. The main focus is on a sample of Asymptotic Giant Branch stars that were selected on their near-infrared colors. Our sample is constructed in such a way to follow the evolution from low mass-loss Mira-type AGB star to high mass-loss rate OH/IR stars. Special emphasis is placed on the transition to the superwind phase. We study the 5-38 \mum spectroscopy, to identify the dust components and molecular species present. In the majority of our sample, the chemistry is oxygen-rich, and we can follow the formation and evolution of dust in the outflow of AGB stars. We will present a first analysis of these spectra. At least two of the stars in our sample show the characteristics of a carbon-rich chemistry. Eventually, we aim to make a comparison with Galactic sources, in order to identify the physical conditions that determine dust properties such as composition and degree of crystallinity.
Support for this work was provided by NASA through the Spitzer Fellowship Program, under award 011 808-001.
Bulletin of the American Astronomical Society, 37 #2
© 2005. The American Astronomical Soceity.