Spectroscopic Analysis of Two Carbon‐rich Post–Asymptotic Giant Branch Stars

Abstract

The chemical compositions of the C-rich post-asymptotic giant branch (pAGB) stars IRAS 05113+1347 and IRAS 22272+5424 are determined from high-resolution optical spectra using standard LTE model atmosphere-based techniques. The stars are C, N, and s-process enriched, suggesting efficient operation of the third dredge-up in the AGB star following a first dredge-up that increased the N abundance. Lithium is present with an abundance requiring Li manufacture. With this pair, abundance analyses are now available for 11 C-rich pAGBs. A common history is indicated and, in particular, the s-abundances, especially the relative abundances of light to heavy s-process elements, follow recent predictions for the third dredge-up in AGB stars.