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arXiv 1005.2363astro-ph.GA
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半人马座球状星团的锰丰度

Manganese Abundances in the Globular Cluster Omega Centauri

Katia Cunha, Verne V. Smith, Maria Bergemann, Nicholas B. Suntzeff, David L. Lambert

摘要:

我们目前的锰丰度在10个红巨星成员的球状星团欧米茄半人马座; 8颗恒星是从最贫金属的人口(RGB MP和RGB MInt 1),而两个目标是成员的金属更丰富的群体(RGB MInt 2和MInt 3)。这是第一次在这个特殊的恒星系统中研究Mn丰度。欧米茄Cen中[Mn/Fe]的LTE值与贫金属欧米茄Cen中银河系恒星的LTE值重叠([Fe/H] ~ -1.5至-1.8),但与在银河系晕和盘星中观察到的不同,[Mn/Fe]在两个更富金属的RGB MInt 2和MInt 3目标中下降。进行非LTE计算,以获得对LTE Mn丰度的校正。Omega Cen的非LTE结果与银河系获得的非LTE [Mn/Fe]与[Fe/H]趋势相比,证实并加强了Omega Cen中锰行为独特的结论。这些结果表明,II型或Ia型的低金属丰度超新星(金属丰度< -2)主导了欧米茄Cen中金属丰度更高的恒星的富集。低金属丰度恒星在欧米茄Cen化学演化中的主导地位已经在S-过程元素中被注意到,其中贫金属AGB恒星的富集被指示。此外,铜也具有金属丰度依赖性产量,在RGB MInt 2和MInt 3 Omega Cen群体中表现出较低的[Cu/Fe]值。

英文摘要:

We present manganese abundances in 10 red-giant members of the globular cluster Omega Centauri; 8 stars are from the most metal-poor population (RGB MP and RGB MInt1) while two targets are members of the more metal rich groups (RGB MInt2 and MInt3). This is the first time Mn abundances have been studied in this peculiar stellar system. The LTE values of [Mn/Fe] in Omega Cen overlap those of Milky Way stars in the metal poor Omega Cen populations ([Fe/H] ~ -1.5 to -1.8), however unlike what is observed in Milky Way halo and disk stars, [Mn/Fe] declines in the two more metal-rich RGB MInt2 and MInt3 targets. Non-LTE calculations were carried out in order to derive corrections to the LTE Mn abundances. The non-LTE results for Omega Cen in comparison with the non-LTE [Mn/Fe] versus [Fe/H] trend obtained for the Milky Way confirm and strengthen the conclusion that the manganese behavior in Omega Cen is distinct. These results suggest that low-metallicity supernovae (with metallicities < -2) of either Type II or Type Ia dominated the enrichment of the more metal-rich stars in Omega Cen. The dominance of low-metallicity stars in the chemical evolution of Omega Cen has been noted previously in the s-process elements where enrichment from metal-poor AGB stars is indicated. In addition, copper, which also has metallicity dependent yields, exhibits lower values of [Cu/Fe] in the RGB MInt2 and MInt3 Omega Cen populations.

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