Element enhancements along the entire asymptotic giant branch phase

The results of a study of the asymptotic giant branch (AGB) phase of stellar evolution are presented. Abundances have been determined for Fe, C, O, the light s-process elements, Y and Zr, the heavy s-process elements, La and Nd, and the r-process element, Eu. The expected relationship between enhanced C, increasing C/O ratio, and enhanced s-process elements has been quantified. Results are presented to provide observational data with which to compare theoretical predictions. The results in this paper confirm previously suggested relationships between C, C/O, and s-process element enhancements. It is seen that AGB stars show C/O ratios from C/O ∼ 0.4 to 1.0, while C enhancements lie between [C/Fe] = 0.1-0.9 dex. Enhancements of s-process elements are as much as [s/Fe] ∼ 1.0 dex for the stars in which C is also greatly enhanced.