The following document lists the file abstract/PROCHE_STARDUST.abs
from catalogue VI/111.
A plain copy of the file
(without headers/trailers) may be downloaded.
Infrared spectra of dusty stellar envelopes reflect the abundances of dust grains and/or large molecules in the circumstellar material and the effects of the stellar radiation field. Prominent emission bands due to silicon carbide or silicate grains are commonly seen in cool giants, reflecting the carbon-rich or oxygen-rich chemistry of the circumstellar material. Carbon-rich dust heated by hot stars (> about 10000 K) often displays emission in the familiar UIR bands which resembles the emission from NGC 7027 or other C-rich planetary nebulae (although significant differences in relative intensities and band profiles are evident from source to source). In contrast some dusty envelopes around cooler stars (in the range 6000-8000 K) display peculiar emission spectra which appear to be related to the UIR emission bands, but which may arise from species that do not survive the harsher radiation fields of the hotter stars, and may therefore represent emission from much more fragile carbon clusters. We wish to investigate the detailed dust emission spectra of a sample of stars which have been found to have peculiar emission features from ground-based and/or IRAS LRS spectra. These consist of a group of 4 post-AGB stars, a Carbon star/A star binary system and an Ae/Be star exciting reflection nebulosity which appears to have a particularly pure UIR emission spectrum. The post-AGB stars seem to form a sequence of increasing departure from the `standard' UIR band spectrum and show a strong broad emission complex at 11-13 microns together with weaker features near 10.5 microns and a prominent emission peak near 21 microns. Ground-based spectra show evidence of substructure in the 21 micron band and we wish to follow this up with higher resolution and higher quality spectra with ISO. ISO provides the only way to sample the whole 2.4 - 45 micron region of these intriguing objects