CS 22957-027: A carbon-rich extremely-metal-poor star
| dc.creator | Bonifacio, P. | |
| dc.creator | Molaro, P. | |
| dc.creator | Beers, T. C. | |
| dc.creator | Vladilo, G. | |
| dc.date | 1997-12-17 | |
| dc.date.accessioned | 2026-07-07T02:25:37Z | |
| dc.date.available | 2026-07-07T02:25:37Z | |
| dc.description | We present a high-resolution spectroscopic analysis of the extremely-metal-poor star CS 22957-027, which Beers et al (1992) noted to exhibit a rather strong G-band. For Teff = 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 about 2 dex relative to the solar value, similar to the handful of other carbon-rich metal-deficient stars discussed by Norris et al (1997a) and Barbuy et al (1997). From the 12C13C (1,0) Swan bandhead and 13CH lines the isotope ratio 12C/13C is about 10, indicating a 13C enrichment. Nitrogen is also found to be enhanced by about 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 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 13CH 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 13C is present. | |
| dc.description | Accepted by A&A, 10 pages, 5 figures, uses l-aa and psfig | |
| dc.identifier | https://arxiv.org/abs/astro-ph/9712227 | |
| dc.identifier | http://arxiv.org/abs/astro-ph/9712227 | |
| dc.identifier.uri | http://salesiana.dossiersoluciones.com/handle/123456789/11944 | |
| dc.subject | Astrophysics | |
| dc.title | CS 22957-027: A carbon-rich extremely-metal-poor star | |
| dc.type | text |