Screening Effects on Electron Capture Rates and Type Ia Supernova Nucleosynthesis
Screening Effects on Electron Capture Rates and Type Ia Supernova Nucleosynthesis
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DOI：
10.3847/1538-4357/abbb32
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发表时间：
2020-09
期刊：
影响因子：
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通讯作者：
Kanji Mori;Toshio Suzuki;M. Honma;M. Famiano;T. Kajino;M. Kusakabe;A. Balantekin
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文献类型：
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作者：
Kanji Mori;Toshio Suzuki;M. Honma;M. Famiano;T. Kajino;M. Kusakabe;A. Balantekin
Ia型超新星（SNe Ia）被认为是一个白色矮星的热核爆炸，但其祖先的质量仍然是一个悬而未决的问题。在超新星Ia的近M Ch模型中，中心密度达到109 g cm−3。电子化学势变得高于fp-壳层核之间的电子捕获（EC）跃迁的Q值，因此一部分可用电子被铁族元素捕获，从而形成富中子同位素。由于EC反应速率对密度敏感，因此中子化程度是区分近M Ch模型和亚M Ch模型的关键。为了比较观察和理论模型，EC反应的准确处理是必要的。然而，在以往的理论工作中，电子屏蔽对EC的影响被忽略。屏蔽降低了EC速率，从而导致更高的电子分数。我们实现电子屏蔽EC计算爆炸SN Ia核合成近M CH单简并模型。结果表明，考虑屏蔽效应后，46，48 Ca，50 Ti，54 Cr，58 Fe，64 Ni和67，70 Zn等丰中子核丰度降低。其中，50 Ti，54 Cr和58 Fe特别令人感兴趣，因为这些核的太阳丰度的很大一部分被认为来自SNe Ia。我们的结论是，在现代超新星Ia模型中实施屏蔽效应的EC是可取的，以精确计算丰中子核素的丰度。
Type Ia supernovae (SNe Ia) are believed to be a thermonuclear explosion of a white dwarf, but the mass of their progenitors is still an open problem. In near-Chandrasekhar-mass (near-M Ch) models of SNe Ia, the central density reaches ≳109 g cm−3. The electron chemical potential becomes higher than the Q-values of electron capture (EC) transitions between fp-shell nuclei, so a portion of the available electrons is captured by iron group elements and thus neutron-rich isotopes are formed. Since EC reaction rates are sensitive to the density, the degree of neutronization is a key to distinguish near- and sub-M Ch models. In order to compare observations and theoretical models, an accurate treatment of EC reactions is necessary. In previous theoretical works, however, effects of electron screening on ECs are ignored. Screening lowers EC rates and thus leads to a higher electron fraction. We implement electron screening on ECs to calculate explosive SN Ia nucleosynthesis in a near-M Ch single degenerate model. It is found that some of neutron-rich nuclear abundances, namely, those of 46,48Ca, 50Ti, 54Cr, 58Fe, 64Ni, and 67,70Zn, decrease when screening effects on ECs are considered. Of these, 50Ti, 54Cr, and 58Fe are particularly interesting because a significant portion of the solar abundance of these nuclei is presumed to originate from SNe Ia. We conclude that implementing the screening effect on ECs in modern SN Ia models is desirable to precisely calculate abundances of neutron-rich nuclides.