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Paper: Silicates as Probes of the Mass Loss History of Oxygen-Rich Evolved Stars
Volume: 196, Thermal Emission Spectroscopy and Analysis of Dust, Disks, and Regoliths
Page: 15
Authors: Kemper, F.; Sylvester, R. J.; Barlow, M. J.; Waters, L. B. F. M.; de Jong, T.; Molster, F. J.; Tielens, A. G. G. M.
Abstract: Combined LWS and SWS observations (2.4 - 197 μm), obtained with the Infrared Space Observatory (ISO), provide a good coverage of the spectral energy distribution (SED) of the circumstellar dust shells of oxygen-rich evolved stars. The spectra of our sample of oxygen-rich stars with mass loss rates ranging from 10-7 - 10-4 Modot yr-1 exhibit a wealth of crystalline and amorphous silicate features. For increasing mass loss rates, we find that the crystalline silicate features become more pronounced. In two objects we find the presence of crystalline silicates in emission and amorphous silicates in absorption at the same wavelength, indicating a difference in spatial distribution of the two species; spherically symmetric and an axi-symmetric geometries are examined.
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