X-shooter 光谱库（XSL）的化学表征：[Mg/Fe] 与 [Ca/Fe] 丰度
Chemical characterisation of the X-shooter Spectral Library (XSL): [Mg/Fe] and [Ca/Fe] abundances
AI总结：
本文利用 GAUGUIN 代码分析 XSL DR2 中 611 颗恒星的中等分辨率光谱，获得 192 颗恒星的 [Mg/Fe] 和 217 颗恒星的 [Ca/Fe] 高精度丰度，结果与 Gaia DR3 和 AMBRE 一致，可用于改进含经验 α 增强的恒星族演化模型。
摘要：
X-shooter 光谱库（XSL）是一个大型经验恒星库，被用作恒星族模型开发的基准。纳入 α 元素丰度对于厘清任何恒星系统的化学演化至关重要。本文旨在提供一份高精度、高准确度的镁和钙丰度星表，这些丰度来自赫罗（HR）图中分布广泛的各种恒星。我们最初对 XSL 数据发布 2 中 611 颗恒星的中等分辨率光谱进行了 Mg 和 Ca 丰度分析。为此，我们使用 GAUGUIN 自动丰度估计代码拟合紫外-蓝（UVB）和可见光（VIS）光谱。我们检验了大气参数和化学丰度与 Gaia DR3 及 AMBRE 项目数据集的一致性。最终，我们分别获得了 192 颗和 217 颗恒星的精确 [Mg/Fe] 和 [Ca/Fe] 丰度，其中 174 颗恒星同时具有两种元素的测量值。这些恒星覆盖了较广的有效温度范围 4000 < T_eff < 6500 K，表面重力范围 0.3 < log(g) < 4.8 cm s^-2，以及金属丰度范围 -2.5 < [Fe/H] < +0.4 dex。我们发现这些丰度估计与 AMBRE:HARPS 和 Gaia/RVS（视向速度光谱仪）的分析结果具有极好的一致性。此外，所得丰度再现了贫金属区间的平台特征，随后即使在超太阳金属丰度下也呈现下降趋势，这与银河系化学演化模型的预测一致。该星表适用于利用经验 α 增强改进演化恒星族模型的建模，这可能在不久的将来对外部星系丰度分析作出重要贡献。
英文摘要：
The X-shooter Spectral Library (XSL) is a large empirical stellar library used as a benchmark for the development of stellar population models. The inclusion of $α$-elements abundances is crucial to disentangling the chemical evolution of any stellar system. The aim of this paper is to provide a catalogue of high-precision and accurate magnesium and calcium abundances from a wide variety of stars well distributed in the Hertzsprung-Russell (HR) diagram. We originally performed an analysis of the derived Mg and Ca abundances for medium-resolution spectra of 611 stars from the XSL Data Release 2. For this purpose, we used the GAUGUIN automated abundance estimation code to fit the ultraviolet-blue (UVB) and visible (VIS) spectra. We tested the consistency of the atmospheric parameters and chemical abundances with the Gaia DR3 and the AMBRE Project datasets. We have finally obtained precise [Mg/Fe] and [Ca/Fe] abundances for 192 and 217 stars respectively, from which 174 stars have measurements in both elements. The stars cover a broad range of effective temperature 4000 < T$_{\rm eff}$ < 6500K, surface gravity 0.3 < log(g) < 4.8 cm s$^{\rm -2}$, and metallicity -2.5 < [Fe/H] < +0.4 dex. We find an excellent agreement with the abundance estimates from the AMBRE:HARPS and the Gaia/RVS (Radial Velocity Spectrometer) analysis. Moreover, the resulting abundances reproduce a plateau in the metal-poor regime followed by a decreasing trend even at supersolar metallicities, as predicted by Galactic chemical evolution models. This catalogue is suitable for improving the modelling of evolutionary stellar population models with empirical $α$-enhancements, which could significantly contribute to the analysis of external galaxies abundances in the near future.
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