The mass range of carbon stars

Abstract

This paper considers the existence of a population of carbon stars that is more massive than that described by Claussen et al. (1987) (1.2-1.6 solar mass). These more massive stars are characterized by molecular envelopes that expand at velocities V-infinity not less than 17.5 km/s and confinemenet to low Galactic latitude. An exponential fit to height above the Galactic plane demonstrates that the carbon stars with high V-infinity are described by a smaller scale height, 107 pc, than that which characterizes carbon stars with low V-infinity, 270 pc. A 100-pc scale height is characteristic of main-sequence stars of mass not less than 2.5-4 solar masses. The larger ratio of 12 to 2 micron fluxes for high V-infinity carbon stars as compared with other carbon stars demonstrates that the former group is more dust obscured. Based on the incidence of optical designations, H-alpha emission, and the 12-micron/2-micron ratio, the stars with larger V-infinity generally have larger mass-loss rates and might dominate the mass returned by carbon stars to the ISM. 33 refs.