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首页> 外文期刊>The Astrophysical Journal. Letters >Super-solar Metallicity Stars in the Galactic Center Nuclear Star Cluster: Unusual Sc, V, and Y Abundances
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Super-solar Metallicity Stars in the Galactic Center Nuclear Star Cluster: Unusual Sc, V, and Y Abundances

机译：银河中心核星群中超级太阳能金属恒星：不寻常的SC，V和Y丰富

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摘要

We present adaptive-optics assisted near-infrared high-spectral-resolution observations of late-type giants in the nuclear star cluster of the Milky Way. The metallicity and elemental abundance measurements of these stars offer us an opportunity to understand the formation and evolution of the nuclear star cluster. In addition, their proximity to the supermassive black hole (~0.5 pc) offers a unique probe of the star formation and chemical enrichment in this extreme environment. We observed two stars identified by medium spectral-resolution observations as potentially having very high metallicities. We use spectral-template fitting with the PHOENIX grid and Bayesian inference to simultaneously constrain the overall metallicity, [M/H], alpha-element abundance [α/Fe], effective temperature, and surface gravity of these stars. We find that one of the stars has very high metallicity ([M/H] > 0.6) and the other is slightly above solar metallicity. Both Galactic center stars have lines from scandium (Sc), vanadium (V), and yttrium (Y) that are much stronger than allowed by the PHOENIX grid. We find, using the spectral synthesis code Spectroscopy Made Easy, that [Sc/Fe] may be an order of magnitude above solar. For comparison, we also observed an empirical calibrator in NGC 6791, the highest metallicity cluster known ([M/H] ~ 0.4). Most lines are well matched between the calibrator and the Galactic center stars, except for Sc, V,and Y, which confirms that their abundances must be anomalously high in these stars. These unusual abundances,which may be a unique signature of nuclear star clusters, offer an opportunity to test models of chemical enrichment in this region.
机译：我们在银河系中核心星集群中展示了自适应 - 光学辅助近红外高光谱分辨率观察。这些恒星的金属性和元素丰富测量为我们提供了理解核星集群的形成和演变的机会。此外，它们对超迹体黑洞（〜0.5cc）的邻近，在这极其环境中提供了明星形成和化学富集的独特探头。我们观察到中谱分辨率观察结果鉴定的两颗恒星，其具有非常高的金属性。我们使用凤凰网格和贝叶斯推理的光谱模板拟合同时约束这些恒星的整体金属性，[m / h]，α元素丰度[α/ Fe]，有效温度和表面重力。我们发现其中一个恒星具有非常高的金属性（[M / H]> 0.6），另一个恒星略高于太阳能金属性。银河系中心恒星都有来自钪（Sc），钒（v）和钇（y）的线，比凤凰网格的允许更强大。我们发现，使用频谱综合码光谱，即[SC / Fe]可以是太阳能高于太阳能的数量级。为了比较，我们还观察到NGC 6791中的经验校准剂，已知的最高金属簇（[M / H]〜0.4）。除了SC，V和Y外，大多数线条之间的匹配良好匹配，除了SC，V和Y，这证实了它们的丰富在这些恒星中的丰富。这些不寻常的大量可能是核星团的独特签名，为该地区测试化学浓缩模式提供了机会。

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