从氦星形成黑洞
Formation of black holes from He stars
AI总结：
研究了初始质量5-65倍太阳质量的氦星演化，探讨其预超新星核心结构对爆炸性的影响，发现核心紧凑性与铁核质量随初始质量非单调变化，表明中子星与黑洞边界并非简单质量阈值。
摘要：
大规模的氦星是Ib/c型超新星的潜在前体。理解其最终命运仍是天体物理学的关键问题。本文研究了初始质量从5到65倍太阳质量的氦星演化，重点分析预超新星核心结构以评估其爆炸性。模拟显示，最终核心结构由碳氧核心质量和核心氦燃烧结束时的中心12C质量分数决定，影响碳燃烧性质和对流壳层位置。最后的碳燃烧对流壳层位置决定了碳自由核心质量，限制了铁核质量和致密性。我们发现最终致密性和铁核质量随初始质量呈现非单调变化，表明中子星与黑洞形成的边界并非简单的质量阈值。这是由于核心碳/氖燃烧变为中微子主导。这一过程驱动更强的核心收缩，最终增加铁核质量和最终致密性。相比之下，早期核心氖/氧/硅点火和壳层合并抑制核心收缩，减少铁核质量和最终致密性。我们还讨论了金属度和超射对预超新星核心结构的影响。这些因素可能影响前体的爆炸性。
英文摘要：
Massive He stars are potential candidates of type Ib/c supernova (SN) progenitors. Understanding their final fates remains a key issue in astrophysics. In this work, we investigate the evolution of He stars with initial masses from 5 $M_\odot$ to 65 $M_\odot$, focusing on the presupernova (pre-SN) core structures to assess their explodability. Our simulations indicate that the final core structure is determined by the CO core mass and the central 12C mass fraction at the end of core He burning, affecting the properties of central C-burning and the locations of convective shells. The location of the last convective C-burning shell sets the mass of the C-free core, constraining the iron core mass and compactness. We found that the final compactness and iron core mass exhibit non-monotonic behavior with initial mass, suggesting that the boundary between neutron star and black hole formation is not a simple mass threshold. This is due to core C/Ne burning becoming neutrino dominated. This process drives stronger core contraction, ultimately increasing the iron core mass and the final compactness. In contrast, earlier core Ne/O/Si ignition and shell mergers inhibit core contraction, reducing both the iron core mass and final compactness. We also discuss the effects of metallicity and overshooting on the pre-SN core structure. These factors potentially affect the explodability of progenitors.
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