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Paper: The Hobby-Eberly Telescope Chemical Abundances of Stars in the Halo (CASH) Project II. The Li-, r- and s-Enhanced Metal-Poor Giant HK-II 17435-00532
Volume: 393, New Horizons in Astronomy: Frank N. Bash Symposium 2007
Page: 207
Authors: Frebel, A.; Roederer, I.U.; Shetrone, M.; Allende Prieto, C.; Rhee, J.; Gallino, R.; Bisterrzo, S.; Sneden, C.; Beers, T.C.; Cowan, J.J.
Abstract: We present the first detailed abundance analysis of the metal-poor giant HK-II 17435-00532. This star was observed as part of the University of Texas Long-Term Chemical Abundances of Stars in the Halo (CASH) Project. We find that this metal-poor ([Fe/H] = −2.2) star has an unusually high lithium abundance (log ε (Li) = +2.1), mild carbon ([C/Fe] = +0.7) and sodium ([Na/Fe] = +0.6) enhancement, as well as enhancement of both s-process ([Ba/Fe] = +0.8) and r-process ([Eu/Fe] = +0.5) material. The high Li abundance can be explained by self-enrichment through extra mixing mechanisms. If so, HK-II 17435-00532 is the most metal-poor star in which this short-lived phase of Li enrichment has been observed. The r- and s-process material was not produced in this star but was either present in the gas from which HK-II 17435-00532 formed or was transferred to it from a more massive binary companion. Despite the current non-detection of radial velocity variations (over a time span of ∼ 180 days), it is possible that HK-II 17435-00532 is in a long-period binary system, similar to other stars with both r and s enrichment.
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