Carbon Stars and Interstellar Dust

Abstract

Extensive recent infrared observations of carbon stars (Gillet et al. 1971, Hackwell 1972, Morrison and Simon 1973) have shown that spectra of some cool variable carbon stars reveal infrared excesses, which are believed to be due to thermal radiation of the dust envelopes surrounding these stars. Observations of the visual intrinsic polarization made by Dyck et al. (1971) have confirmed this discovery. The relation existing between stars loosing their mass and those revealing the infrared excess (Geisel 1970) gives evidence for the reality of mass loss from cool variable carbon stars. On the other hand, several investigations (Kamijo 1967, Donn et al. 1968, Salpeter 1974), although differing considerably in details, do agree that conditions in the atmospheres of cool carbon stars are appropriate for the condensation of carbon grains. Hence, it is believed that evolutionary advanced cool variable carbon stars supply carbonaceous material, mainly graphite, into the interstellar matter, in which carbon seems to be the major constituent (Donn et al. 1968).