Circumstellar environments: Pt. 4

The band strengths of 11.2μm SiC features in IRAS spectra have been determined for a number of carbon stars whose mass-loss rates have been determined earlier from the COJ=2→1 or J=1→0 emission lines. The strength of the 11.2μm SiC feature is proportional to the total mass-loss rate (as measured from CO), supporting the idea that the gas-to-dust ratio is roughly constant for carbon stars. This therefore provides an easy method of calculating mass-loss rates for carbon stars which are too distant to be detected in CO. The observed correlation probably also indicates that the ratios of carbon to silicon carbide grains in the outflows increase with age. (author)