从光谱丰度到恒星模型中的演化[α/Fe]
From spectroscopic abundances to evolutionary [$α$/Fe] in stellar models
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- Institute of Space Sciences (ICE, CSIC)（空间科学研究所）
- Institut d’Estudis Espacials de Catalunya (IEEC)（加泰罗尼亚空间研究学院）
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中文总结 AI 辅助
针对现有恒星模型化学丰度描述简化的问题，提出微扰方法与演化α增强概念，推出工具ALCHEMY，可利用光谱丰度计算恒星演化相关的[α/Fe]ₑᵥ。
中文摘要 AI 辅助
大规模高分辨率光谱巡天绘制了数百万颗恒星的详细化学丰度模式，但恒星演化模型与等时线库仍依赖化学丰度的简化描述，通常假设为太阳标度成分或所有α元素的恒定增丰。此外，α增丰的定义因巡天而异，未必是与恒星结构和演化最相关的量。在精确恒星天体物理学时代，恒星模型需更好地利用光谱巡天提供的丰富化学信息。我们开发了一种微扰方法，用于计算具有任意α元素模式的恒星演化轨迹；通过多项式展开量化恒星演化轨迹对单个α元素变化的响应，可将这些响应线性组合以生成给定丰度模式的合成轨迹。我们还提出了演化α增强[α/Fe]ₑᵥ，即所有α元素的恒定增强，可再现观测丰度模式对恒星模型的影响。我们利用具有详细APOGEE丰度的恒星验证了两种方法，并量化了不同巡天中光谱[α/Fe]与[α/Fe]ₑᵥ的差异；确定了精确恒星模型所需的最小化学元素集，并推出了简单快速的工具ALCHEMY，用于计算一般α元素丰度模式的[α/Fe]ₑᵥ。
英文摘要
Large-scale, high-resolution spectroscopic surveys map detailed chemical abundance patterns for millions of stars. However, libraries of stellar evolution models and isochrones still rely on a simplified description of chemical abundances, generally assuming either solar-scaled compositions or a constant enrichment for all $α$-elements. Moreover, the definition of $α$-enrichment is survey-dependent and is not necessarily the most relevant quantity for stellar structure and evolution. In the era of precision stellar astrophysics, stellar models need to better account for the wealth of chemical information provided by spectroscopic surveys. We develop a perturbative method to compute stellar evolution tracks for stars with arbitrary patterns of $α$-elements. We quantify the response of stellar evolutionary tracks to variations of individual $α$-elements through polynomial expansions, which can be linearly combined to produce synthetic tracks for a given abundance pattern. We also introduce the evolutionary $α$-enhancement, [$α$/Fe]$_{\rm ev}$, a constant enhancement for all $α$-elements that reproduces the impact of an observed abundance pattern on stellar models. We validate both methods using stars with detailed APOGEE abundances and quantify the differences between spectroscopic [$α$/Fe] and [$α$/Fe]$_{\rm ev}$ for different surveys. We identify a minimal set of chemical elements required for accurate stellar models and present ALCHEMY, a simple and fast tool to compute [$α$/Fe]$_{\rm ev}$ for general $α$-element abundance patterns.
