Ten-Micron Observations of Bright Circumstellar Shells-Spectral Properties and a Search for Extended Emission.

摘要

A 9-14 micron spectra are obtained for several bright long-period variable stars, using novel instrumentation comprising a mosaic detector array and a prism slit spectrometer. Three of the stars are carbon rich and have SiC feature emission. The remaining five are oxygen rich; three exhibit pronounced silicate emission. Agreement is found in the SiC equivalent widths for the three carbon stars observed here and during the 1983 flight of the IRAS low-resolution spectrometer. Two stars with silicate feature emission observed at both epochs, IRAS + 10420 and mu Cep, show pronounced variation in the equivalent widths of these features. Continuum variations are observed exceeding the photometric levels of uncertainty for either instrument for the carbon star V Cyg with which correlate well with visible light curves. None of the circumstellar shells of these stars were fully resolved; only IRC + 10420 may be partially resolved. The observed upper limits on surface brightness of dust associated with molecular outflows from IRC + 10216 are compatible with calculated lower limits, yielding no additional constrains on the depressed dust emission suggested by far-infrared detections of the outflow material. Keywords: Infrared, Spectroscopy, Circumstellar shells, Infrared sources, Reprints. (jhd)