Comparison of Photospheric and Circumstellar (HCN)/(CO)-Ratios for Bright Carbon Stars

摘要

Measures of circumstellar HCN/CO abundance ratios for carbon stars are compared with corresponding ratios estimated from photospheric abundance analysis. A satisfactory agreement is found for most stars. However, V Hya and two 60 micrometer-excess sources have significantly lower circumstellar ratios than expected, and for the (13)C-rich stars the ratios are somewhat higher.