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Titolo:
CS-22957-027 - A CARBON-RICH EXTREMELY-METAL-POOR STAR
Autore:
BONIFACIO P; MOLARO P; BEERS TC; VLADILO G;
Indirizzi:
OSSERV ASTRON TRIESTE,VIA GB TIEPOLO 11 I-34131 TRIESTE ITALY MICHIGAN STATE UNIV,DEPT PHYS & ASTRON E LANSING MI 48824
Titolo Testata:
Astronomy and astrophysics
fascicolo: 2, volume: 332, anno: 1998,
pagine: 672 - 680
SICI:
0004-6361(1998)332:2<672:C-ACES>2.0.ZU;2-G
Fonte:
ISI
Lingua:
ENG
Soggetto:
CH STARS; MASS STARS; ABUNDANCES; SEARCH; BARIUM;
Keywords:
STARS, INDIVIDUAL, CS 22957-027; STARS, ABUNDANCES; STARS, CARBON; STARS, POPULATION II; GALAXY, HALO;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
37
Recensione:
Indirizzi per estratti:
Citazione:
P. Bonifacio et al., "CS-22957-027 - A CARBON-RICH EXTREMELY-METAL-POOR STAR", Astronomy and astrophysics, 332(2), 1998, pp. 672-680

Abstract

We present a high-resolution spectroscopic analysis of the extremely-metal-poor star CS 22957-027, which Beers et ai. (1992) noted to exhibit a rather strong G-band. For T-eff = 4839 K, derived from broadband photometry, our analysis obtains log g = 2.25, and a very low metallicity of [Fe/H]=-3.43 +/- 0.12. The carbon-to-iron ratio is found to be enhanced by approximate to 2 dex relative to the solar value, similar to the handful of other carbon-rich metal-deficient stars discussed byNorris et al. (1997a) and Barbuy et al. (1997). From the (CC)-C-12-C-13 (1,0)Swan bandhead and (CH)-C-13 lines the isotope ratio C-12/C-13 is approximate to 10, indicating a C-13 enrichment. Nitrogen is also found to be enhanced by approximate to 1 dex. The s- process elements Sr and Ba are, surprisingly, found to be under-abundant relative to solar, with [Sr/Fe]=-0.91 and [Ba/Fe]=-0.93. The star's low luminosity requires that the chemical enrichment arises from mass transfer from an evolved companion rather than self-polluting dredge-up up processes. However, the s- process elements Sr and Ba are unusually low, with a solar ratio to one another, at variance with what found in the ''classical'' CH stars. Finally we note that a feature due to (CH)-C-13 is present in coincidence with the Th II 401.9129 nm resonance line. The blend is of relevance for the nucleo-chronology use of the Th II line in these extremely metal poor stars, when significant C-13 is present.

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Documento generato il 19/09/20 alle ore 15:27:54