使用 GENEC 将大质量恒星演化至核心坍缩：状态方程、不透明度及有效核反应网络的扩展
Evolving massive stars to core collapse with GENEC: Extension of equation of state, opacities and effective nuclear network
AI总结：
本文扩展 GENEC 的状态方程、核反应网络及不透明度，构建 15–25 倍太阳质量前身星模型，并验证其可用于核心坍缩与超新星动力学研究。
摘要：
初始质量约高于 8 倍太阳质量的恒星将演化形成一个由铁族元素组成的核心，此时带电核之间不再有进一步的放热核反应能够阻止核心坍缩。电子俘获、中微子损失以及重核的光致解离会触发这些恒星的坍缩。处于核心坍缩边缘的模型由恒星演化程序生成，这些坍缩前模型可用于研究随后的动力学演化（包括它们作为超新星爆发以及形成中子星或黑洞等致密遗迹）。我们升级了 GENeva 恒星演化程序（GENeva stellar Evolution Code，GENEC）所采用的物理要素，使其能够覆盖生成核心坍缩前身星所需的高温和高密度区域。我们从三个方面改进了 GENEC：状态方程、核反应网络，以及适用于演化晚期计算的辐射不透明度和传导不透明度。我们生成了一个小规模的超新星前身星模型网格，其中恒星的零龄主序质量为 15、20 和 25 倍太阳质量，金属丰度分别为太阳金属丰度和不足一半太阳金属丰度。所得结果与使用 MESA 程序生成的同类模型进行了比较。我们新模型的整体性质，尤其是其内核的性质，与 MESA 计算的模型以及文献中已有的前身星相当。不同程序之间确切的壳层结构存在差异，从而影响爆发预测。通过采用最先进物理要素的 GENEC，我们生成了坍缩前的大质量恒星前身星。这些前身星适合后续研究，包括动力学坍缩和超新星阶段。更大规模的超新星前身星网格现在已具备可行性，并具有进一步开展动力学演化研究的潜力。
英文摘要：
Stars with initial mass above roughly 8 solar masses will evolve to form a core made of iron group elements at which point no further exothermic nuclear reactions between charged nuclei may prevent the core collapse. Electron captures, neutrino losses, and the photo-disintegration of heavy nuclei trigger the collapse of these stars. Models at the brink of core collapse are produced using stellar evolution codes and these pre-collapse models may be used in the study of the subsequent dynamical evolution (including their explosion as supernovae and the formation of compact remnants such as neutron stars or black holes). We upgrade the physical ingredients employed by the GENeva stellar Evolution Code, GENEC, so that it may cover the regime of high temperatures and high densities required to produce progenitors of core-collapse. We have improved GENEC in three directions, equation of state, the nuclear reaction network and the radiative and conductive opacities adapted for the computation of the advanced phases of evolution. We produce a small grid of pre-supernova models of stars with zero-age main sequence masses of 15, 20 and 25 solar masses at solar and less than half solar metallicities. The results are compared with analogous models produced with the MESA code. The global properties of our new models, particularly of their inner cores, are comparable to models computed with MESA and pre-existing progenitors in the literature. Between codes the exact shell structure varies impacting explosion predictions. Using GENEC with state-of-the-art physics, we have produced massive stellar progenitors prior to collapse. These progenitors are suitable for follow-up studies, including the dynamical collapse and supernova phases. Larger grids of supernova progenitors are now feasible, with potential for further dynamical evolution.
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