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arXiv 0909.0179nucl-th
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恒星核坍缩过程中电子俘获率的改进估计

Improved estimate of electron capture rates on nuclei during stellar core collapse

A. Juodagalvis, K. Langanke, W. R. Hix, G. Martínez-Pinedo, J. M. Sampaio

摘要:

在导致超新星爆炸的大质量恒星坍缩核心的动力学中,原子核上的电子俘获起着重要的作用。这些捕获率的最近计算是基于微观模型,占相关的自由度。由于计算的限制,这种计算仅限于适度数量的原子核,主要在质量范围A=45-110。最近的超新星模拟表明,这个核池,然而,省略了非常丰富的中子和重的核,占主导地位的核组成在最后阶段的坍缩中微子捕获之前。假设组成是由核统计平衡,我们在这里提出的电子捕获率的崩溃条件来自约2700个单独的核的个别率。对于那些在早期阶段的崩溃占主导地位的核,在微观模型的框架内导出的个别率,而对于占主导地位的核在高密度的基础上,我们推导出的速率与单粒子占据数的全局参数化的随机相位近似。此外,我们通过适当地包括对反应速率的筛选校正来改进先前的速率评估。

英文摘要:

Electron captures on nuclei play an important role in the dynamics of the collapsing core of a massive star that leads to a supernova explosion. Recent calculations of these capture rates were based on microscopic models which account for relevant degrees of freedom. Due to computational restrictions such calculations were limited to a modest number of nuclei, mainly in the mass range A=45-110. Recent supernova simulations show that this pool of nuclei, however, omits the very neutron-rich and heavy nuclei which dominate the nuclear composition during the last phase of the collapse before neutrino trapping. Assuming that the composition is given by Nuclear Statistical Equilibrium we present here electron capture rates for collapse conditions derived from individual rates for roughly 2700 individual nuclei. For those nuclei which dominate in the early stage of the collapse, the individual rates are derived within the framework of microscopic models, while for the nuclei which dominate at high densities we have derived the rates based on the Random Phase Approximation with a global parametrization of the single particle occupation numbers. In addition, we have improved previous rate evaluations by properly including screening corrections to the reaction rates into account.

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