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The Chemical Composition of Carbon-Rich , Very Metal-Poor Stars : A New Class of Mildly Carbon-Rich Objects Without Excess of Neutron-Capture Elements
| Content Provider | Semantic Scholar |
|---|---|
| Author | Aoki, Wako Ando, Hiroyasu |
| Copyright Year | 2001 |
| Abstract | We report on an analysis of the chemical composition of five carbon-rich, very metalpoor stars based on high-resolution spectra. One star, CS 22948-027, exhibits very large overabundances of carbon, nitrogen, and the neutron-capture elements, as found in the previous study of Hill et al.. This result may be interpreted as a consequence of mass transfer from a binary companion that previously evolved through the asymptotic giant branch stage. By way of contrast, the other four stars we investigate exhibit no overabundances of barium ([Ba/Fe]< 0), while three of them have mildly enhanced carbon and/or nitrogen ([C+N]∼+1). We have been unable to determine accurate carbon and nitrogen abundances for the remaining star (CS 30312-100). These stars are rather similar to the carbon-rich, neutron-capture-element-poor star CS 22957-027 discussed previously by Norris et al., though the carbon overabundance in this object is significantly larger ([C/Fe]= +2.2). Our results imply that these carbon-rich objects with “normal” neutron-capture element abundances are not rare among very metaldeficient stars. One possible process to explain this phenomenon is as a result of helium shell flashes near the base of the AGB in very low-metallicity, low-mass (M . 1M⊙) stars, as recently proposed by Fujimoto et al.. The moderate carbon enhancements reported herein ([C/Fe]∼ +1) are similar to those reported in the famous r-process-enhanced star CS 22892-052. We discuss the possibility that the same process might be responsible for this similarity, as well as the implication that a completely independent phenomenon was responsible for the large r-process enhancement in CS 22892-052. Subject headings: nuclear reactions, nucleosynthesis – stars: abundances – stars: AGB and post-AGB – stars: carbon – stars: Population II National Astronomical Observatory, Mitaka, Tokyo, 181-8588 Japan; email: aoki.wako@nao.ac.jp, ando@optik.mtk.nao.ac.jp Research School of Astronomy & Astrophysics, The Australian National University, Private Bag, Weston Creek Post Office, Canberra, ACT 2611, Australia; email: jen@mso.anu.edu.au Department of Physics & Astronomy, The Open University, Walton Hall, Milton Keynes, MK7 6AA, UK; email: s.g.ryan@open.ac.uk Department of Physics & Astronomy, Michigan State University, East Lansing, MI 48824-1116; email: beers@pa.msu.edu |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | http://arxiv.org/pdf/astro-ph/0111297v1.pdf |
| Language | English |
| Access Restriction | Open |
| Subject Keyword | Astronomy Bands Barium Carbon Monoxide Poisoning Coupling (computer programming) Dietary Iron Dr. Sbaitso Elements Email Emoticon Exhibits as Topic Fallopia multiflora plant Field electron emission GUCY2C protein, human Gene Ontology Term Enrichment Gigantism Helium IBM Notes Ikeda map Image resolution Large Like button Medical Subject Headings Nephrogenic Systemic Fibrosis Neutrons Offset binary Phenylpropanolamine Physical object Seventy Nine Stars, Celestial TI-Nspire series The Australian |
| Content Type | Text |
| Resource Type | Article |
