The extremely metal-poor, neutron capture-rich star CS 22892-052: A comprehensive abundance analysis

被引:460
作者
Sneden, C
Cowan, JJ
Lawler, JE
Ivans, II
Burles, S
Beers, TC
Primas, F
Hill, V
Truran, JW
Fuller, GM
Pfeiffer, B
Kratz, KL
机构
[1] Univ Texas, Dept Astron, Austin, TX 78712 USA
[2] Univ Texas, McDonald Observ, Austin, TX 78712 USA
[3] Univ Oklahoma, Dept Phys & Astron, Norman, OK 73019 USA
[4] Univ Wisconsin, Dept Phys, Madison, WI 53706 USA
[5] MIT, Dept Phys, Cambridge, MA 02139 USA
[6] Michigan State Univ, Dept Phys & Astron, E Lansing, MI 48824 USA
[7] European So Observ, D-85748 Garching, Germany
[8] Observ Meudon, GEPI, F-92195 Meudon, France
[9] Univ Chicago, Enrico Fermi Inst, Dept Astron & Astrophys, Chicago, IL 60637 USA
[10] Univ Calif San Diego, Dept Phys, La Jolla, CA 92093 USA
[11] Johannes Gutenberg Univ Mainz, Inst Kernchem, D-55099 Mainz, Germany
关键词
Galaxy : abundances; Galaxy : evolution; Galaxy : halo; nuclear reactions; nucleosynthesis; abundances; stars : abundances; stars : Population II;
D O I
10.1086/375491
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
High-resolution spectra obtained with three ground-based facilities and the Hubble Space Telescope (HST) have been combined to produce a new abundance analysis of CS 22892-052, an extremely metal-poor giant with large relative enhancements of neutron capture elements. A revised model stellar atmosphere has been derived with the aid of a large number of Fe peak transitions, including both neutral and ionized species of six elements. Several elements, including Mo, Lu, Au, Pt, and Pb, have been detected for the first time in CS 22892-052, and significant upper limits have been placed on the abundances of Ga, Ge, Cd, Sn, and U in this star. In total, abundance measurements or upper limits have been determined for 57 elements, far more than previously possible. New Be and Li detections in CS 22892-052 indicate that the abundances of both these elements are significantly depleted compared to unevolved main-sequence turnoff stars of similar metallicity. Abundance comparisons show an excellent agreement between the heaviest n-capture elements (Z greater than or equal to 56) and scaled solar system r-process abundances, confirming earlier results for CS 22892-052 and other metal-poor stars. New theoretical r-process calculations also show good agreement with CS 22892-052 abundances and the solar r-process abundance components. The abundances of lighter elements (40 less than or equal to Z less than or equal to 50), however, deviate from the same scaled abundance curves that match the heavier elements, suggesting different synthesis conditions or sites for the low-mass and high-mass ends of the abundance distribution. The detection of Th and the upper limit on the U abundance together imply a lower limit of 10.4 Gyr on the age of CS 22892-052, quite consistent with the Th/Eu age estimate of 12.8 +/- similar or equal to3 Gyr. An average of several chronometric ratios yields an age 14.2 +/- similar or equal to 3 Gyr.
引用
收藏
页码:936 / 953
页数:18
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