Abundance analysis of r+s stars: R-process abundance comparison between r+s stars and r-rich stars

摘要

The chemical abundances of the r + s stars can give us excellent information for setting constraints on models of s- and r-process nucleosynthesis. In this article, we fit the element abundances of 32 r + s or s-rich stars by using a parametric model.We find that the r-process abundance pattern related to r + s stars is similar to the pattern of r-rich stars. On the other hand, the abundance pattern of light elements and iron group elements for the r + s stars is very close to the pattern for weak r-process stars. The r + s stars and r-rich stars are initially formed in the molecular cloud, which had been polluted by weak r-process material. The yields of r-process related to r + s stars are proportional to their metallicity. Although the origin and site of the s-process are quite different from those of the r-process, there is a strong correlation between the enhancement level of the s-process and r-process in r + s stars. This implies that r-process matter accreted from the origin of the r-process, such as AIC or SN 1.5, has an increasing trend with increasing s-process matter accreted from the AGB stars.