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Carbon-Enhanced Metal-Poor Stars. Osmium and Iridium Abundances in the Neutron-Capture-Enhanced Subgiants CS31062-050 and LP625-44

Wako Aoki·Sara Bisterzo·Roberto Gallino·Timothy C. Beers·John E. Norris·Sean G. Ryan·Stelios Tsangarides
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Abstract

We have investigated the abundances of heavy neutron-capture elements, including osmium (Os) and iridium (Ir), in the two Carbon-Enhanced Metal-Poor (CEMP) subgiants CS31062-050 and LP625-44. CS31062-050 is known to be a so-called CEMP-r/s star, which exhibits large excesses of s-process elements such as barium (Ba) and lead (Pb), as well as a significant enhancement of europium (Eu) that cannot be explained by conventional s-process production in Asymptotic Giant Branch star models. Our analysis of the high-resolution spectrum for this object has determined, for the first time, the abundances of Ir and Os, elements in the third peak of the r-process nucleosynthesis. They also exhibit significant excesses relative to the predictions of standard s-process calculations. These two elements are not detected in a similar-quality spectrum of LP625-44; the derived upper limits on their abundances are lower than the abundances in CS31062-050. We compare the observed abundance patterns of neutron-capture elements, including Os and Ir, in these two stars with recent model calculations of the s-process, and discuss possible interpretations.

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Wako Aoki, Sara Bisterzo, Roberto Gallino, Timothy C. Beers, John E. Norris, Sean G. Ryan, Stelios Tsangarides. 2006-09-06. Carbon-Enhanced Metal-Poor Stars. Osmium and Iridium Abundances in the Neutron-Capture-Enhanced Subgiants CS31062-050 and LP625-44. https://doi.org/10.1086/508878

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