帮助理解大质量恒星演化中因果关系的数值实验
Numerical experiments to help understand cause and effect in massive star evolution
AI总结：
本文提出SNAPSHOT建模方法，通过数值恒星结构模型研究大质量恒星演化中内部丰度分布对表面性质、超巨星类型及蓝回路的因果影响，并揭示低金属丰度恒星更致密的机制。
摘要：
大质量恒星的演化受到多种物理过程的影响，包括对流、旋转、质量损失和双星相互作用。由于这些过程会以多种方式同时改变恒星内部的化学丰度分布，因此确定恒星内部的哪些性质主要驱动整体演化可能具有挑战性。在先前工作的基础上，我们开发了一种名为SNAPSHOT的新建模方法，该方法使我们能够分离出驱动大质量恒星演化的内部丰度分布的关键特征。利用我们的方法，我们计算了覆盖恒星演化关键阶段的热平衡数值恒星结构模型。对于主序阶段，我们证明了具有相同质量和非常相似表面性质的模型可以具有不同的内部氢分布和对流核心质量。我们讨论了大质量恒星在主序之后膨胀的原因，以及它们变成红超巨星、蓝超巨星或黄超巨星的根本原因。对于主序后阶段，我们证明了丰度分布的微小变化可以对表面性质产生非常大的影响。我们还讨论了产生蓝超巨星的效应以及蓝回路的成因。我们的模型表明，金属丰度较低的大质量恒星往往更加致密，这是由于燃烧区域中较低的CNO丰度和包层中较低的不透明度的综合效应。
英文摘要：
The evolution of massive stars is affected by a variety of physical processes including convection, rotation, mass loss and binary interaction. Because these processes modify the internal chemical abundance profiles in multiple ways simultaneously, it can be challenging to determine which properties of the stellar interior are primarily driving the overall evolution. Building on previous work, we develop a new modelling approach called SNAPSHOT that allows us to isolate the key features of the internal abundance profile that drive the evolution of massive stars. Using our approach, we compute numerical stellar structure models in thermal equilibrium covering key phases of stellar evolution. For the main sequence, we demonstrate that models with the same mass and very similar surface properties can have different internal distributions of hydrogen and convective core masses. We discuss why massive stars expand after the main sequence and the fundamental reasons for why they become red, blue or yellow supergiants. For the post-main sequence, we demonstrate that small changes in the abundance profile can cause very large effects on the surface properties. We also discuss the effects that produce blue supergiants and the cause of blue loops. Our models show that massive stars with lower metallicity tend to be more compact due to the combined effect of lower CNO abundances in the burning regions and lower opacity in the envelope.
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