The s ‐Process in Metal‐Poor Stars: Abundances for 22 Neutron‐Capture Elements in CS 31062‐050

Abstract

The CH star CS 31062-050 (Fe/H=-2.42) is one of the most useful stars yet discovered for evaluating the s-process in metal-poor stars. It is very abundant in heavy elements (e.g., La/Fe=2.2), and its relatively cool temperature and low gravity mean that there are many lines of interesting elements present in the spectrum. We measured the abundances of 22 elements with Z>29, including the rarely measured Lu and Pd. We derive an upper limit on the Th abundance as well. The abundances in CS 31062-050 show a similar pattern to many other metal-poor CH stars: high Pb/Fe and Pb/La ratios, low Y/La ratios and high Eu/La values compared to the solar system s-process. However, the Th limit, with additional assumptions, is not consistent with the idea that the excess Eu in CS 31062-050 is contributed by the r-process. In addition, the observed Eu/Tb cannot be explained by any ratio of solar-system s-process and r-process abundances. We therefore argue that the abundance pattern in CS 31062-050 is most likely the result of the s-process, and we discuss possible modifications that could explain the non-solar-system pattern observed.