标题： 恒星大气层 显示英文标题

标题： Stellar Atmospheres

摘要： 恒星在我们的宇宙中起着决定性的作用，从宇宙的开始一直到其完整的演化过程。 为了全面理解它们的特性、演化以及外层包层的物理性质，需要通过与大气的数值模型进行比较来分析恒星光谱。 我们讨论如何计算这些模型的基础（特别是密度和温度分层，受低质量恒星中对流能量传输的影响），这需要同时处理流体力学、热力学和辐射转移。 我们强调发射率、不透明度以及特别是它们的比值（源函数）的影响，并总结了这些量是如何计算的，无论是采用还是放松局部热力学平衡（LTE）的假设。 随后，我们讨论恒星风的影响和物理性质（以及它们的各种驱动机制作为恒星类型的函数）、旋转、磁场、不均匀性和多体性。 最后，我们概述了定量光谱学的基础，即如何在实践中分析观测到的光谱。 显示英文摘要

摘要： Stars play a decisive role in our Universe, from its beginning throughout its complete evolution. For a thorough understanding of their properties, evolution, and physics of their outer envelopes, stellar spectra need to be analyzed by comparison with numerical models of their atmospheres. We discuss the foundations of how to calculate such models (in particular, density and temperature stratification, affected by convective energy transport in low-mass stars), which requires a parallel treatment of hydrodynamics, thermodynamics and radiative transfer. We stress the impact of emissivities, opacities, and particularly their ratio (source function), and summarize how these quantities are calculated, either adopting or relaxing the assumption of LTE (local thermodynamic equilibrium). Subsequently, we discuss the influence and physics of stellar winds (and their various driving mechanisms as a function of stellar type), rotation, magnetic fields, inhomogeneities, and multiplicity. Finally, we outline the basics of quantitative spectroscopy, namely how to analyze observed spectra in practice.