In Pop III stellar models convection-induced mixing between H- and He-rich burning layers can induce a burst of nuclear energy and thereby substantially alter the subsequent evolution and nucleosynthesis in the first massive stars. We investigate H-He shell and core interactions in 26 stellar evolution simulations with masses $15 - 140 \,\mathrm{M}_{\odot}$, using five sets of mixing assumptions. In 22 cases, H-He interactions induce local nuclear energy release in the range $ \sim 10^{9} - 10^{13.5}\, \mathrm{L}_{\odot}$. The luminosities on the upper end of this range amount to a substantial fraction of the layer's internal energy over a convective advection timescale, indicating a dynamic stellar response that would violate 1D stellar evolution modelling assumptions. We distinguish four types of H-He interactions depending on the evolutionary phase and convective stability of the He-rich material. H-burning conditions during H-He interactions give $^{12}\mathrm{C}/^{13}\mathrm{C}$ ratios between $\approx 1.5$ to $\sim1000$ and [C/N] ratios from $\approx -1.7 $ to $\approx 3.2$ with a correlation that agrees well with observations of CEMP-no stars. We also explore Ca production from hot CNO breakout and find the simulations presented here likely cannot explain the observed Ca abundance in the most Ca-poor CEMP-no star. We describe the evolution leading to H-He interactions, which occur during or shortly after core-contraction phases. Three simulations without a H-He interaction are computed to Fe-core infall and a $140\,\mathrm{M}_{\odot}$ simulation becomes pair-unstable. We also discuss present modelling limitations and the need for 3D hydrodynamic models to fully understand these stellar evolutionary phases.

中文翻译：

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大量人口 III 恒星演化模型中的对流 H-He 相互作用

在 Pop III 恒星模型中，对流引起的富氢和富氦燃烧层之间的混合可以引起核能爆发，从而大大改变第一批大质量恒星的后续演化和核合成。我们使用五组混合假设研究了质量为 $15 - 140 \,\mathrm{M}_{\odot}$ 的 26 个恒星演化模拟中的 H-He 壳和核心相互作用。在 22 种情况下，H-He 相互作用导致局部核能释放 $\sim 10^{9} - 10^{13.5}\, \mathrm{L}_{\odot}$。该范围上端的光度在对流平流时间尺度上占该层内部能量的很大一部分，表明动态恒星响应将违反一维恒星演化建模假设。我们根据富 He 材料的演化阶段和对流稳定性区分了四种类型的 H-He 相互作用。H-He 相互作用期间的 H-燃烧条件给出 $^{12}\mathrm{C}/^{13}\mathrm{C}$ 比率在 $\approx 1.5$ 到 $\sim1000$ 和 [C/N] 比率之间从 $\approx -1.7 $ 到 $\approx 3.2$，相关性与 CEMP-no 恒星的观测非常吻合。我们还探索了从热 CNO 爆发中产生的 Ca，并发现此处提供的模拟可能无法解释在最缺乏 Ca 的 CEMP 无星中观察到的 Ca 丰度。我们描述了导致 H-He 相互作用的演变，它发生在核心收缩阶段期间或之后不久。三个没有 H-He 相互作用的模拟被计算为 Fe-core infall，$140\,\mathrm{M}_{\odot}$ 模拟变得对不稳定。