AN ELEMENTAL ASSAY OF VERY, EXTREMELY, AND ULTRA-METAL-POOR STARS
We present a high-resolution elemental-abundance analysis for a sample of 23 very metal-poor ([Fe/H] < −2.0) stars, 12 of which are extremely metal-poor ([Fe/H] < −3.0), and 4 of which are ultra-metal-poor ([Fe/H] < −4.0). These stars were targeted to explore differences in the abundance ra...
| Main Authors: | , , , , , , , , , , |
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| Other Authors: | |
| Format: | Article |
| Language: | en_US |
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IOP Publishing
2015
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| Online Access: | http://hdl.handle.net/1721.1/98359 https://orcid.org/0000-0002-2139-7145 |
| _version_ | 1826201920407076864 |
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| author | Hansen, T. Hansen, C. J. Christlieb, N. Beers, T. C. Yong, D. Bessell, M. S. Placco, V. M. Norris, J. E. Asplund, M. Frebel, Anna L. Perez Garcia, A. E. |
| author2 | Massachusetts Institute of Technology. Department of Physics |
| author_facet | Massachusetts Institute of Technology. Department of Physics Hansen, T. Hansen, C. J. Christlieb, N. Beers, T. C. Yong, D. Bessell, M. S. Placco, V. M. Norris, J. E. Asplund, M. Frebel, Anna L. Perez Garcia, A. E. |
| author_sort | Hansen, T. |
| collection | MIT |
| description | We present a high-resolution elemental-abundance analysis for a sample of 23 very metal-poor ([Fe/H] < −2.0) stars, 12 of which are extremely metal-poor ([Fe/H] < −3.0), and 4 of which are ultra-metal-poor ([Fe/H] < −4.0). These stars were targeted to explore differences in the abundance ratios for elements that constrain the possible astrophysical sites of element production, including Li, C, N, O, the α-elements, the iron-peak elements, and a number of neutron-capture elements. This sample substantially increases the number of known carbon-enhanced metal-poor (CEMP) and nitrogen-enhanced metal-poor (NEMP) stars—our program stars include eight that are considered "normal" metal-poor stars, six CEMP-no stars, five CEMP-s stars, two CEMP-r stars, and two CEMP-r/s stars. One of the CEMP-r stars and one of the CEMP-r/s stars are possible NEMP stars. We detect lithium for three of the six CEMP-no stars, all of which are Li depleted with respect to the Spite plateau. The majority of the CEMP stars have [C/N] > 0. The stars with [C/N] < 0 suggest a larger degree of mixing; the few CEMP-no stars that exhibit this signature are only found at [Fe/H] < −3.4, a metallicity below which we also find the CEMP-no stars with large enhancements in Na, Mg, and Al. We confirm the existence of two plateaus in the absolute carbon abundances of CEMP stars, as suggested by Spite et al. We also present evidence for a "floor" in the absolute Ba abundances of CEMP-no stars at A(Ba) ~ −2.0. |
| first_indexed | 2024-09-23T11:58:57Z |
| format | Article |
| id | mit-1721.1/98359 |
| institution | Massachusetts Institute of Technology |
| language | en_US |
| last_indexed | 2024-09-23T11:58:57Z |
| publishDate | 2015 |
| publisher | IOP Publishing |
| record_format | dspace |
| spelling | mit-1721.1/983592022-10-01T07:24:55Z AN ELEMENTAL ASSAY OF VERY, EXTREMELY, AND ULTRA-METAL-POOR STARS Hansen, T. Hansen, C. J. Christlieb, N. Beers, T. C. Yong, D. Bessell, M. S. Placco, V. M. Norris, J. E. Asplund, M. Frebel, Anna L. Perez Garcia, A. E. Massachusetts Institute of Technology. Department of Physics MIT Kavli Institute for Astrophysics and Space Research Frebel, Anna L. We present a high-resolution elemental-abundance analysis for a sample of 23 very metal-poor ([Fe/H] < −2.0) stars, 12 of which are extremely metal-poor ([Fe/H] < −3.0), and 4 of which are ultra-metal-poor ([Fe/H] < −4.0). These stars were targeted to explore differences in the abundance ratios for elements that constrain the possible astrophysical sites of element production, including Li, C, N, O, the α-elements, the iron-peak elements, and a number of neutron-capture elements. This sample substantially increases the number of known carbon-enhanced metal-poor (CEMP) and nitrogen-enhanced metal-poor (NEMP) stars—our program stars include eight that are considered "normal" metal-poor stars, six CEMP-no stars, five CEMP-s stars, two CEMP-r stars, and two CEMP-r/s stars. One of the CEMP-r stars and one of the CEMP-r/s stars are possible NEMP stars. We detect lithium for three of the six CEMP-no stars, all of which are Li depleted with respect to the Spite plateau. The majority of the CEMP stars have [C/N] > 0. The stars with [C/N] < 0 suggest a larger degree of mixing; the few CEMP-no stars that exhibit this signature are only found at [Fe/H] < −3.4, a metallicity below which we also find the CEMP-no stars with large enhancements in Na, Mg, and Al. We confirm the existence of two plateaus in the absolute carbon abundances of CEMP stars, as suggested by Spite et al. We also present evidence for a "floor" in the absolute Ba abundances of CEMP-no stars at A(Ba) ~ −2.0. National Science Foundation (U.S.) (CAREER Grant AST-1255160) 2015-09-03T17:47:31Z 2015-09-03T17:47:31Z 2015-07 2015-03 Article http://purl.org/eprint/type/JournalArticle 1538-4357 0004-637X http://hdl.handle.net/1721.1/98359 Hansen, T., C. J. Hansen, N. Christlieb, T. C. Beers, D. Yong, M. S. Bessell, A. Frebel, et al. “AN ELEMENTAL ASSAY OF VERY, EXTREMELY, AND ULTRA-METAL-POOR STARS.” The Astrophysical Journal 807, no. 2 (July 9, 2015): 173. © 2015 The American Astronomical Society https://orcid.org/0000-0002-2139-7145 en_US http://dx.doi.org/10.1088/0004-637X/807/2/173 The Astrophysical Journal Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use. application/pdf IOP Publishing IOP Publishing |
| spellingShingle | Hansen, T. Hansen, C. J. Christlieb, N. Beers, T. C. Yong, D. Bessell, M. S. Placco, V. M. Norris, J. E. Asplund, M. Frebel, Anna L. Perez Garcia, A. E. AN ELEMENTAL ASSAY OF VERY, EXTREMELY, AND ULTRA-METAL-POOR STARS |
| title | AN ELEMENTAL ASSAY OF VERY, EXTREMELY, AND ULTRA-METAL-POOR STARS |
| title_full | AN ELEMENTAL ASSAY OF VERY, EXTREMELY, AND ULTRA-METAL-POOR STARS |
| title_fullStr | AN ELEMENTAL ASSAY OF VERY, EXTREMELY, AND ULTRA-METAL-POOR STARS |
| title_full_unstemmed | AN ELEMENTAL ASSAY OF VERY, EXTREMELY, AND ULTRA-METAL-POOR STARS |
| title_short | AN ELEMENTAL ASSAY OF VERY, EXTREMELY, AND ULTRA-METAL-POOR STARS |
| title_sort | elemental assay of very extremely and ultra metal poor stars |
| url | http://hdl.handle.net/1721.1/98359 https://orcid.org/0000-0002-2139-7145 |
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