The chemical compositions of stars encode the history of the universe and are thus fundamental for advancing our knowledge of astrophysics and cosmology. However, measurements of elemental abundance ratios, and our interpretations of them, strongly depend on the physical assumptions that dictate the generation of synthetic stellar spectra. Three-dimensional radiation-hydrodynamic (3D RHD) box-in-a-star simulations of stellar atmospheres offer a more realistic representation of surface convection occurring in late-type stars than do traditional one-dimensional (1D) hydrostatic models. As evident from a multitude of observational tests, the coupling of 3D RHD models with line formation in nonlocal thermodynamic equilibrium (non-LTE) today provides a solid foundation for abundance analysis for many elements. This review describes the ongoing and transformational work to advance the state of the art and replace 1D LTE spectrum synthesis with its 3D non-LTE counterpart. In summary: ▪3D and non-LTE effects are intricately coupled, and consistent modeling thereof is necessary for high-precision abundances; such modeling is currently feasible for individual elements in large surveys. Mean 3D (〈3D〉) models are not adequate as substitutes.▪The solar abundance debate is presently dominated by choices and systematic uncertainties that are not specific to 3D non-LTE modeling.▪3D non-LTE abundance corrections have a profound impact on our understanding of FGK-type stars, exoplanets, and the nucleosynthetic origins of the elements.

中文翻译：

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晚型恒星的三维非局域热力学平衡丰度分析


恒星的化学成分编码了宇宙的历史，因此对于推进我们的天体物理学和宇宙学知识至关重要。然而，元素丰度比的测量以及我们对它们的解释，在很大程度上取决于决定合成恒星光谱产生的物理假设。与传统的一维 （1D） 静水模型相比，恒星大气的三维辐射流体动力学 （3D RHD） 箱式恒星模拟可以更真实地表示晚期恒星中发生的表面对流。从大量的观测测试中可以明显看出，3D RHD 模型与当今非局部热力学平衡 （non-LTE） 中的谱线形成的耦合为许多元素的丰度分析提供了坚实的基础。本综述介绍了正在进行的变革性工作，以推进最先进的技术，并用 3D 非 LTE 频谱合成取代 1D LTE 频谱合成。总之：▪3D 和非 LTE 效应错综复杂地耦合在一起，对于高精度丰度，需要对其进行一致的建模;目前，这种建模对于大型调查中的单个元素是可行的。平均 3D （〈3D〉） 模型不足以替代。▪太阳丰度的争论目前由选择和系统不确定性主导，这些选择和不确定性并非特定于 3D 非 LTE 建模。▪3D 非 LTE 丰度校正对我们对 FGK 型恒星、系外行星和元素的核合成起源的理解有着深远的影响。