Contents of: VI/111/./abstract/SKWOK_21MICADD.abs

The following document lists the file abstract/SKWOK_21MICADD.abs from catalogue VI/111.
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==> In this proposal, more time is being requested for SKWOK.21MICRON
==> This proposal requests an upgrade from Priority 3 for SKWOK.21MICRON
The IRAS Satellite discovered a small number of sources with an unidentified
emission feature at 21 microns (Kwok, Volk, and Hrivnak, 1989).  Currently this
feature has been confirmed only in F- and G-type supergiant stars with large
infrared excesses, and almost all 21 micron sources have been identified as
stars in the transition from the asymptotic giant branch to the planetary
nebula phase.  Although many suggestions have been made on the possible
carrier of this feature, its origin remains unknown.
Optical spectroscopy of the stars with the 21 micron feature has shown that
they are carbon-rich, and most of them display the strong near-infrared PAH
bands but their band ratios are different from other PAH sources.  In this
proposal, we request ISO observations to (1) confirm new 21 micron sources
which we have selected from previous ground-based observations; and (2) to
obtain high spectral resolution observations to search for possible fine
structures in this broad feature. These observations will provide solid
constraints on any dust carrier molecule and we hope that it will lead to an
eventual identification of its carrier.