The Hobby-Eberly Telescope Chemical Abundances Of Stars In The Halo (CASH) Project. I. The Lithium-, s-, And r-Enhanced Metal-Poor Giant HKII 17435-00532

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dc.contributor.utaustinauthorRoederer, Ian U.en_US
dc.contributor.utaustinauthorFrebel, Annaen_US
dc.contributor.utaustinauthorShetrone, Matthew D.en_US
dc.contributor.utaustinauthorPrieto, Carlos Allendeen_US
dc.contributor.utaustinauthorSneden, Christopheren_US
dc.creatorRoederer, Ian U.en_US
dc.creatorFrebel, Annaen_US
dc.creatorShetrone, Matthew D.en_US
dc.creatorPrieto, Carlos Allendeen_US
dc.creatorRhee, Jaehyonen_US
dc.creatorGallino, Robertoen_US
dc.creatorBisterzo, Saraen_US
dc.creatorSneden, Christopheren_US
dc.creatorBeers, Timothy C.en_US
dc.creatorCowan, John J.en_US
dc.date.accessioned2016-04-28T19:37:29Z
dc.date.available2016-04-28T19:37:29Z
dc.date.issued2008-06en
dc.description.abstractWe present the first detailed abundance analysis of the metal-poor giant HKII 17435-00532. This star was observed as part of the University of Texas long-term project Chemical Abundances of Stars in the Halo ( CASH). A spectrum was obtained with the High Resolution Spectrograph (HRS) on the Hobby-Eberly Telescope with a resolving power of R similar to 15,000. Our analysis reveals that this star may be located on the red giant branch, red horizontal branch, or early asymptotic giant branch. We find that this metal-poor (Fe/H = -2.2) star has an unusually high lithium abundance [log epsilon(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 that connects the convective envelope with the outer regions of the H-burning shell. If so, HKII 17435-00532 is the most metal-poor star in which this short-lived phase of Li enrichment has been observed. The Na and n-capture enrichment can be explained by mass transfer from a companion that passed through the thermally pulsing AGB phase of evolution with only a small initial enrichment of r-process material present in the birth cloud. Despite the current nondetection of radial velocity variations (over similar to 180 days), it is possible that HKII 17435 - 00532 is in a long-period or highly inclined binary system, similar to other stars with similar n-capture enrichment patterns.en_US
dc.description.departmentAstronomyen_US
dc.description.sponsorshipNASA AAS Small Research Grant Programen_US
dc.description.sponsorshipGALEX GI 05-GALEX05-27en_US
dc.description.sponsorshipItalian MIUR-PRIN06 Projecten_US
dc.description.sponsorshipNSF AST 06-07708, AST04-06784, AST 07-0776, PHY 02-15783en_US
dc.description.sponsorshipJINA AST 07-07447en_US
dc.identifierdoi:10.15781/T22V4T
dc.identifier.Filename2008_06_hkii17435-00532.pdfen_US
dc.identifier.citationRoederer, Ian U., Anna Frebel, Matthew D. Shetrone, Carlos Allende Prieto, Jaehyon Rhee, Roberto Gallino, Sara Bisterzo, Christopher Sneden, Timothy C. Beers, and John J. Cowan. "The Hobby-Eberly Telescope Chemical Abundances of Stars in the Halo (CASH) Project. I. The Lithium-, s-, and r-enhanced Metal-poor Giant HKII 17435ﾖ00532." The Astrophysical Journal, Vol. 679, No. 2 (Jun., 2008): 1549.en_US
dc.identifier.doi10.1086/587794en_US
dc.identifier.issn0004-637Xen_US
dc.identifier.urihttp://hdl.handle.net/2152/34942
dc.language.isoEnglishen_US
dc.relation.ispartofen_US
dc.relation.ispartofserialAstrophysical Journalen_US
dc.rightsAdministrative deposit of works to Texas ScholarWorks: This works author(s) is or was a University faculty member, student or staff member; this article is already available through open access or the publisher allows a PDF version of the article to be freely posted online. The library makes the deposit as a matter of fair use (for scholarly, educational, and research purposes), and to preserve the work and further secure public access to the works of the University.en_US
dc.rights.restrictionOpenen_US
dc.subjectnuclear reactions, nucleosynthesis, abundancesen_US
dc.subjectstars : abundancesen_US
dc.subjectstars : individual (hkii 17435-00532)en_US
dc.subjectstars : population iien_US
dc.subjectneutron-capture elementsen_US
dc.subjectmass red giantsen_US
dc.subjecthigh-dispersion-spectrographen_US
dc.subjecteffective temperature scaleen_US
dc.subjectnear-ultraviolet observationsen_US
dc.subjecthorizontal-branch starsen_US
dc.subjectgalactic haloen_US
dc.subjectprocess nucleosynthesisen_US
dc.subjectspectroscopic analysisen_US
dc.subjectoscillator-strengthsen_US
dc.subjectastronomy & astrophysicsen_US
dc.titleThe Hobby-Eberly Telescope Chemical Abundances Of Stars In The Halo (CASH) Project. I. The Lithium-, s-, And r-Enhanced Metal-Poor Giant HKII 17435-00532en_US
dc.typeReviewen_US

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