Europium, Samarium, And Neodymium Isotopic Fractions In Metal-Poor Stars

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dc.contributor.utaustinauthorRoederer, Ian U.en_US
dc.contributor.utaustinauthorSneden, Christopheren_US
dc.contributor.utaustinauthorSobeck, Jennifer S.en_US
dc.creatorRoederer, Ian U.en_US
dc.creatorLawler, James E.en_US
dc.creatorSneden, Christopheren_US
dc.creatorCowan, John J.en_US
dc.creatorSobeck, Jennifer S.en_US
dc.creatorPilachowski, Catherine A.en_US
dc.date.accessioned2016-04-28T19:39:30Z
dc.date.available2016-04-28T19:39:30Z
dc.date.issued2008-03en
dc.description.abstractWe have derived isotopic fractions of europium, samarium, and neodymium in two metal-poor giants with differing neutron-capture nucleosynthetic histories. These isotopic fractions were measured from new high-resolution (R similar to 120; 000), high signal-to-noise ratio (S/N similar to 160-1000) spectra obtained with the 2d-coude spectrograph of McDonald Observatory's 2.7m Smith telescope. Synthetic spectra were generated using recent high-precision laboratory measurements of hyperfine and isotopic subcomponents of several transitions of these elements and matched quantitatively to the observed spectra. We interpret our isotopic fractions by the nucleosynthesis predictions of the stellar model, which reproduces s-process nucleosynthesis from the physical conditions expected in low-mass, thermally pulsing stars on the AGB, and the classical method, which approximates s-process nucleosynthesis by a steady neutron flux impinging on Fe-peak seed nuclei. Our Eu isotopic fraction in HD 175305 is consistent with an r-process origin by the classical method and is consistent with either an r- or an s-process origin by the stellar model. Our Sm isotopic fraction in HD 175305 suggests a predominantly r- process origin, and our Sm isotopic fraction in HD 196944 is consistent with an s-process origin. The Nd isotopic fractions, while consistent with either r-process or s-process origins, have very little ability to distinguish between any physical values for the isotopic fraction in either star. This study for the first time extends the n-capture origin of multiple rare earths in metal-poor stars from elemental abundances to the isotopic level, strengthening the r-process interpretation for HD 175305 and the s-process interpretation for HD 196944.en_US
dc.description.departmentAstronomyen_US
dc.description.sponsorshipNSF AST 03-07279, AST 05-06324, AST 03-07495, AST 06-07708en_US
dc.identifierdoi:10.15781/T2N813
dc.identifier.Filename2008_03_europium.pdfen_US
dc.identifier.citationRoederer, Ian U., James E. Lawler, Christopher Sneden, John J. Cowan, Jennifer S. Sobeck, and Catherine A. Pilachowski. "Europium, Samarium, and Neodymium Isotopic Fractions in Metal-Poor Stars." The Astrophysical Journal, Vol. 675, No. 1 (Mar., 2008): 723.en_US
dc.identifier.doi10.1086/526452en_US
dc.identifier.issn0004-637Xen_US
dc.identifier.urihttp://hdl.handle.net/2152/35046
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.subjectatomic dataen_US
dc.subjectnuclear reactionsen_US
dc.subjectnucleosynthesisen_US
dc.subjectabundancesen_US
dc.subjectstars :en_US
dc.subjectabundancesen_US
dc.subjectstars : population iien_US
dc.subjectneutron-capture elementsen_US
dc.subjectlaboratory transition-probabilitiesen_US
dc.subjecthigh-dispersion-spectrographen_US
dc.subjectgiant branch starsen_US
dc.subjectr-process-richen_US
dc.subjects-process-richen_US
dc.subjectnear-ultraviolet observationsen_US
dc.subjectgalactic chemicalen_US
dc.subjectevolutionen_US
dc.subjecteffective temperature scaleen_US
dc.subjectoscillator-strengthsen_US
dc.subjectastronomy & astrophysicsen_US
dc.titleEuropium, Samarium, And Neodymium Isotopic Fractions In Metal-Poor Starsen_US
dc.typeReviewen_US

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