Circumstellar envelopes and the evolution of carbon stars

Abstract

A quantitative classification scheme is presented for carbon stars that yields temperature class, carbon class, and C13 isotopic index, derived from low-resolution, image-tube scanner spectra. An absolute magnitude and bolometric luminosity calibration is constructed on the basis of temperature class from information existing in the literature. This scheme is applied to 16 carbon stars that have high infrared luminosity and results in spectral classifications; quantitative estimates of circumstellar extinction, both differential and neutral, assuming that small graphite grains are responsible; individual distances; column masses of graphite; intrinsic fluxes of Hα emission; a possible evolutionary sequence. The hypothesis that hydrogen emission is caused by shock waves is vindicated.