r-Process Nucleosynthesis in Magnetohydrodynamic Jet Explosions of Core-Collapse Supernovae
r-Process Nucleosynthesis in Magnetohydrodynamic Jet Explosions of Core-Collapse Supernovae
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DOI：
10.1086/500786
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发表时间：
2005-04
期刊：
影响因子：
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通讯作者：
S. Nishimura;K. Kotake;M. Hashimoto;S. Yamada;N. Nishimura;S. Fujimoto;Katsuhiko Sato
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文献类型：
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作者：
S. Nishimura;K. Kotake;M. Hashimoto;S. Yamada;N. Nishimura;S. Fujimoto;Katsuhiko Sato
我们研究了 13 M☉ 大质量恒星中纯磁流体动力学 (MHD) 爆炸期间的 r 过程核合成。二维 MHD 模拟是从核心塌陷开始到冲击传播到富硅层（弹跳后约 500 毫秒）进行的。此后，利用爆炸过程中的成分，通过温度和密度两种时间外推来计算后期的r过程核合成。通过这些计算，我们表明，与球形爆炸相反，由于快速旋转和强磁场的综合作用而形成的喷射状爆炸显着降低了铁芯中的电子分数。我们证明，从硅层射流中喷射出的低 Ye 材料有利于再现太阳 r 元素图案的第三个峰值。此外，我们还利用完整的核反应网络研究了裂变的影响以及两种质量公式对上述MHD模型中获得的r过程峰的差异。结果，我们发现它们都可以重现直到第三个峰值的全球丰度模式，尽管详细的分布有很大不同。最后，我们讨论了中微子吸收反应（未与上述 MHD 模拟耦合）对上述计算中获得的 Ye 可能还原的影响。我们指出，如果 MHD 效应发挥重要作用，那么超新星爆炸中 r 过程核合成应该存在变化。
We investigate the r-process nucleosynthesis during a purely magnetohydrodynamic (MHD) explosion in a massive star of 13 M☉. The two-dimensional MHD simulations have been carried out from the onset of the core collapse to the shock propagation to the silicon-rich layers (~500 ms after bounce). Thereafter, using the compositions during the explosion, we calculate the r-process nucleosynthesis in the later phase by employing the two kinds of time extrapolations of the temperature and density. With these computations, we show that the jetlike explosion formed due to the combined effects of rapid rotation and strong magnetic field lowers the electron fraction significantly in the iron core, contrary to the spherical explosion. We demonstrate that the ejected material with low Ye in the jet coming out from the silicon layers is good for reproducing the third peak of the solar r-element pattern. In addition, we investigate the effects of fission using the full nuclear reaction network and the differences of two kinds of mass formulae on the r-process peaks obtained in the above MHD models. As a result, we find that both of them can reproduce the global abundance pattern up to the third peaks, although the detailed distributions are rather different. Finally, we discuss the effects of neutrino absorption reactions, which are not coupled to the above MHD simulations, on the possible reduction of Ye obtained in the above computations. We point out that there should be variations in the r-process nucleosynthesis in the supernova explosion if the MHD effects play an important role.