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Session 47 - Circumstellar Disks & Shells.
Display session, Thursday, January 08
We present preliminary results of a study of the spectral emission from oxygen-rich dust. We have observed several evolved stars embedded within circumstellar dust shells using the Short Wavelength Spectrometer aboard the Infrared Space Observatory (ISO). The unprecedented spectral coverage, complete from the near to the far infrared (2-46 \mum), enables us to study the relative strengths and shapes of the well-known 10 and 18 \mum features from silicate dust, the more recently discovered features at 7 and 13 \mum, and new features apparent at other wavelengths. This approach will provide the constraints necessary to identify the mineral constituency of the dust grains responsible for the features.
T Cep and EP Aqr both show a strong 7 \mum feature, which almost certainly arises from an additional dust component, as yet unidentified. In three other sources, this feature has separated into two weaker components. X Pav shows an unusually strong 13 \mum feature, which is also apparent in the spectra of several other sources. The 18 \mum feature separates into three features at 17, 18, and 19.5-20.0 \mum. The strength of this last component follows the 13 \mum feature. Additional spectral features appear at 6.2, 32, 36, and 44 \mum.
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