Estimating R-Process Yields from Abundances of the Metal-Poor Stars

Abstract

The chemical abundances of metal-poor stars provide important clues to explore stellar formation history and set significant constraints on models of the r-process. In this work, we find that the abundance patterns of the light and iron group elements of the main r-process stars are very close to those of the weak r-process stars. Based on a detailed abundance comparison, we find that the weak r-process occurs in supernovae with a progenitor mass range of ∼11–26 M⊙. Using the SN yields given by Heger & Woosley and the abundances of the weak r-process stars, the weak r-process yields are derived. The SNe with a progenitor mass range of 15 M⊙ < M < 26 M⊙ are the main sites of the weak r-process, and their contributions are larger than 80%. Using the abundance ratios of the weak r-process and the main r-process in the solar system, the average yields of the main r-process are estimated. The observed correlations of [neutron-capture/Eu] versus [Eu/Fe] can be explained by mixing of the two r-process abundances in various fractions.