Analysis of the IRAS Low Resolution Spectra

Analysis of the IRAS low resolution spectra show that the 8-22 micron spectral range show a variety of emission features. The strongest features in spectra of M stars are the 10 and 18 micron silicate emission features. In addition a three-component feature with peaks at 10, 11 and 13.1 micron and a weak, broad 9-15 micron feature is present in many M variable stars. Most carbon stars show the 11.2 micron SiC emission feature as well as, in some cases, an unidentified 8-9 micron emission feature. The MS, S and SC stars show a range of emission features whose peaks range from 10 to 11.2 micron. The excess emission above the underlying photospheric continuum in the 8-22 micron region for S Mira variables shows a sharp increase for period greater than about 370 days.