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arXiv 2011.12303astro-ph.GA
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精美光环III的供应商。一个可能的欧米茄Cen伴生矿的化学丰度分析

Purveyors of fine halos III. Chemical abundance analysis of a potential omega Cen associate

Andreas J. Koch-Hansen, Camilla Juul Hansen, Linda Lombardo, Piercarlo Bonifacio, Michael Hanke, Elisabetta Caffau

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9 pages, 6 figures, accepted for publication in Astronomy & Astrophysics
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摘要：

球状星团（GC）是银河系（MW）恒星晕形成的重要贡献者，在银河系历史上贡献了10%的水平。起源于第二代溶解或溶解星团的恒星可以很容易地通过不同的轻元素特征来识别，例如增强的N和Na以及同时耗尽的C和O丰度。在本文中，我们提出了一个广泛的化学丰度分析晕星J110842，这是以前的运动学与大规模MW GC $ω$半人马座（$ω$岑），我们讨论了可行的方案，从逃逸到遇到。基于使用UVES光谱仪的高分辨率，高信噪比光谱，我们能够测量所有核合成通道中的31种元素的33种。这颗恒星的金属丰度[Fe II/H]= $-2.10$ $\pm$ 0.02（统计值）。$\pm0.07$（系统）dex将其置于$ω$ Cen的金属丰度分布的较低的第六个百分位。我们发现，所有的同位素元素丰度，从$α$ -和Fe-峰元素的中子捕获元素是密切兼容的$ω$岑的广泛的丰度分布。然而，考虑到这个天体的丰度与所有MW成分的大部分重叠，这并不允许明确区分恒星的起源。相比之下，我们对CN的增强及其在Na-O关系的Na强轨迹上的位置的测量使我们可以想象它最初是作为第二代GC星形成的，支持了这个晕星与大质量GC $ω$ Cen的前关联。

英文摘要：

Globular clusters (GCs) are important donors to the build-up of the Milky Way (MW) stellar halo, having contributed at the ten percent level over the Galactic history. Stars that originated from the second generation of dissolved or dissolving clusters can be readily identified via distinct light-element signatures such as enhanced N and Na and simultaneously depleted C and O abundances. In this paper we present an extensive chemical abundance analysis of the halo star J110842, which was previously kinematically associated with the massive MW GC $ω$ Centauri ($ω$Cen), and we discuss viable scenarios from escape to encounter. Based on a high-resolution, high signal-to-noise spectrum of this star using the UVES spectrograph, we were able to measure 33 species of 31 elements across all nucleosynthetic channels. The star's low metallicity of [FeII/H]=$-2.10$$\pm$0.02(stat.)$\pm0.07$(sys.) dex places it in the lower sixth percentile of $ω$Cen's metallicity distribution. We find that all of the heavier-element abundances, from $α$- and Fe-peak elements to neutron-capture elements are closely compatible with $ω$Cen's broad abundance distribution. However, given the major overlap of this object's abundances with the bulk of all of the MW components, this does not allow for a clear-cut distinction of the star's origin. In contrast, our measurements of an enhancement in CN and its position on the Na-strong locus of the Na-O anticorrelation render it conceivable that it originally formed as a second-generation GC star, lending support to a former association of this halo star with the massive GC $ω$Cen.

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