SPECTROSCOPIC STUDY OF CARBON STARS WITH SILICATE FEATURES .1. OBSERVATIONS

The results of an optical spectroscopic study of carbon stars with silicate feature done at the Dominion Astrophysical Observatory in Victoria in 1991 is presented. Four stars (CCGCS 1653, CCGCS 4222, CCGCS 4923, and CCGCS 5848) are confirmed to be C-13-rich carbon stars (J stars). Two stars (CCGCS 1158 and CCGCS 4729) are provisionally identified as J stars. A preliminary spectral analysis is carried out. Two groups of J stars were found in the IRAS color-color diagram. The ''red group'' contains carbon stars with silicate emission feature which are good J star candidates; and the ''vertical strip group'' contains standard J stars which show weak or no SiC feature. It is suggested that the sources in the ''red group'' represent the higher mass members of the asymptotic giant branch population. The enhancement of C-13 may be explained by the envelope burning mechanism.