Evolution of ONeMg Core in Super-AGB Stars toward Electron-capture Supernovae: Effects of Updated Electron-capture Rate
Evolution of ONeMg Core in Super-AGB Stars toward Electron-capture Supernovae: Effects of Updated Electron-capture Rate
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DOI：
10.3847/1538-4357/ab4b4b
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发表时间：
2019-07
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影响因子：
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通讯作者：
S. Zha;S. Leung;Toshio Suzuki;K. Nomoto
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作者：
S. Zha;S. Leung;Toshio Suzuki;K. Nomoto
具有∼8-10 M⊙的恒星演化形成一个强烈简并的OneMg核。当核心质量接近钱德拉塞卡质量时，核心经历了24毫克和20Ne的电子俘获，从而引发了电子俘获超新星(ECSN)。为了弄清ECSN是导致坍塌还是导致热核爆炸，我们计算了8.4M⊙星从主序列到氧在其核心内点火的演化过程。我们在20Ne上应用最新的电子俘获速率，包括第二禁带跃迁，并研究了氧点火(中心或偏离中心)的位置和Ye分布如何依赖于输入物理以及对半对流和对流的处理。由于对流的作用，氧爆燃开始时的中心密度ρc，def可以显著高于氧点火时的中心密度，我们估计。我们对火焰传播进行了二维模拟，以检验OneMg核的最终命运如何取决于Ye分布和ρc，def。我们发现，从开始的爆燃导致坍塌(热核爆炸)。由于我们对ρc，def的估计超过了这个临界值，所以OneMg核可能会坍塌，尽管进一步研究爆燃前的对流和半对流是很重要的。
Stars with ∼8–10 M⊙ evolve to form a strongly degenerate ONeMg core. When the core mass becomes close to the Chandrasekhar mass, the core undergoes electron captures on 24Mg and 20Ne that induce an electron-capture supernova (ECSN). In order to clarify whether the ECSN leads to a collapse or thermonuclear explosion, we calculate the evolution of an 8.4 M⊙ star from the main sequence until the oxygen ignition in the ONeMg core. We apply the latest electron-capture rate on 20Ne, including the second forbidden transition, and investigate how the location of the oxygen ignition (center or off-center) and the Ye distribution depend on the input physics and the treatment of the semiconvection and convection. The central density when the oxygen deflagration is initiated, ρc,def, can be significantly higher than that of the oxygen ignition thanks to the convection, and we estimate . We perform two-dimensional simulations of the flame propagation to examine how the final fate of the ONeMg core depends on the Ye distribution and ρc,def. We find that the deflagration starting from leads to a collapse (thermonuclear explosion). Since our estimate of ρc,def exceeds this critical value, the ONeMg core is likely to collapse, although further studies of the convection and semiconvection before the deflagration are important.