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R. B. Reid, A. K. Speck (University of Missouri)
Examining the dust around evolved stars gives information about the end phases of stars' lives. Information obtained from astromineralogy can be used to construct models of how low and intermediate mass stars end their lives, and thus what they provide for the interstellar medium. Using the infrared (IR) spectra of supergiant and asymptotic giant branch (AGB) stars, one can identify the composition and structure of the dust around these stars and then compare that information with laboratory spectra and meteoritic samples to further understand the lifecycle of stellar material. Spectral information about intermediate mass stars in the Milky Way (MW) is good in that the stars are closer and brighter. However, the drawback to observing such stars in our own galaxy is that there is some uncertainty in the distances of these stars. This uncertainty can lead to errors in determining the star’s intrinsic brightness. We are investigating intermediate mass evolved stars in the Magellanic Clouds (MCs), where all of the stars observed are essentially at the same distance, which allows brightness determinations. Another reason to observe stars in the MCs is that the metallicity of MC stars is less than that of those in the Milky Way. This allows us to investigate the effect of metallicity on spectral features, and whether the MC stars’ spectra allow them to be fit into current IR spectral classification schemes. We have a sample of mid-IR spectra of MC stars from ISO. The spectra of these stars are compared with similar MW stars' spectra using classification schemes that are based on prominence of spectral features and shape of the spectrum at certain wavelengths. This approach will demonstrate whether differences in metallicity affect the processes of dust formation around evolved stars, which in turn constrains dust formation mechanisms.
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Bulletin of the American Astronomical Society, 36 5
© 2004. The American Astronomical Society.