HE 1327-2326, An Unevolved Star With Fe/H <-5.0. III. Does Its Atmosphere Reflect Its Natal Composition?

dc.contributor.utaustinauthorFrebel, Annaen_US
dc.creatorKorn, A. J.en_US
dc.creatorRichard, O.en_US
dc.creatorMashonkina, L.en_US
dc.creatorBessell, Michael S.en_US
dc.creatorFrebel, Annaen_US
dc.creatorAoki, Wakoen_US
dc.date.accessioned2016-04-28T19:37:56Z
dc.date.available2016-04-28T19:37:56Z
dc.date.issued2009-06en
dc.description.abstractBased on spectroscopic constraints derived from nonlocal thermodynamic equilibrium line formation, we explore the likely range of stellar parameters (T-eff and log g) for the hyper-metal-poor (HMP) star HE 1327-2326. Combining the constraints from Balmer line profiles and the Ca I/II ionization equilibrium, a subgiant stage of evolution is indicated. This result is further supported by spectrophotometric observations of the Balmer jump. If a higher T-eff value was used (as favored by some photometric calibrations), the spectroscopic analysis would indicate a turnoff-point stage of evolution. Using a stellar-structure code that treats the effects of atomic diffusion throughout the star in detail, we evolve a low-mass model star to reach the Hertzsprung-Russell-diagram position of HE 1327-2326 after roughly 13 Gyr. While the surface abundances are modified significantly (by more than 1 dex for the case of uninhibited diffusion), such corrections cannot resolve the discrepancy between the abundance inferred from the nondetection of the Li I resonance line at 6707 angstrom and the Wilkinson Microwave Anisotropy Probe based primordial lithium abundance. As there are numerous processes that can destroy lithium, any cosmological interpretation of a lower-than-expected lithium abundance at the lowest metallicities will have to await sample sizes of unevolved HMP stars that are 1 order of magnitude larger. The situation remains equally inconclusive concerning atomic-diffusion corrections. Here, attempts have to be made to better constrain internal mixing processes, both observationally and by means of sophisticated modeling. With constraints on additional mixing processes taken from a recent globular-cluster study, the likeliest scenario is that HE 1327-2326's surface abundances have undergone mild depletion (of order 0.2 dex).en_US
dc.description.departmentMcDonald Observatoryen_US
dc.description.sponsorshipSwedish Research Council (Vetenskapradet)en_US
dc.description.sponsorshipPresidium RAS Programme "Origin and evolution of stars and the Galaxy"en_US
dc.description.sponsorshipDeutsche Forschungsgemeinschaft GE 490/34-1en_US
dc.description.sponsorshipW. J. McDonald Fellowship of the McDonald Observatoryen_US
dc.description.sponsorshipJSPS 18104003en_US
dc.identifierdoi:10.15781/T2ZZ4X
dc.identifier.Filename2009_06_he13272326.pdfen_US
dc.identifier.citationKorn, A. J., O. Richard, L. Mashonkina, M. S. Bessell, A. Frebel, and W. Aoki. "He 1327ヨ2326, An Unevolved Star with [Fe/H]<ヨ5.0. III. Does its Atmosphere Reflect its Natal Composition?." The Astrophysical Journal, Vol. 698, No. 1 (Jun., 2009): 410.en_US
dc.identifier.doi10.1088/0004-637x/698/1/410en_US
dc.identifier.issn0004-637Xen_US
dc.identifier.urihttp://hdl.handle.net/2152/34966
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.subjectdiffusionen_US
dc.subjectstars: abundancesen_US
dc.subjectstars: evolutionen_US
dc.subjectstars: fundamentalen_US
dc.subjectparametersen_US
dc.subjectstars: individual (he 1327-2326)en_US
dc.subjectstars: population iien_US
dc.subjectmetal-poor starsen_US
dc.subjectradiative acceleration calculationsen_US
dc.subjectless-than -5.0en_US
dc.subjectnon-lteen_US
dc.subjectwmap observationsen_US
dc.subjectatomic diffusionen_US
dc.subjectline formationen_US
dc.subject1st starsen_US
dc.subjectfgk starsen_US
dc.subjectold starsen_US
dc.subjectastronomy & astrophysicsen_US
dc.titleHE 1327-2326, An Unevolved Star With Fe/H <-5.0. III. Does Its Atmosphere Reflect Its Natal Composition?en_US
dc.typeArticleen_US

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