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arXiv 2103.01909nucl-thastro-ph.SR
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前超新星演化中重要弱相互作用核的研究

Investigation of important weak interaction nuclei in presupernova evolution

Jameel-Un Nabi, Asim Ullah, Ali Abas Khan

摘要:

该项目旨在研究大质量恒星超新星前演化过程中最重要的弱相互作用核。为了达到这一目标,考虑了一个包含728个原子核的系综,其质量范围为A = 1- 100。我们计算了这些核的质量分数使用Saha的方程为预定值的\textit{$T$},\textit{$ρ$}和\textit{$Y_e$},并假设核统计平衡。使用新引入的配方,其中激发态,高达10 $MeV$,被视为离散的核配分函数。弱相互作用速率(电子俘获(\textit{ec})和$β$ -衰变(\textit{bd}))是在\textit{totally}微观方式中使用质子-中子准粒子无规相位近似(pn-QRPA)模型计算的,不假设Brink-Axel假设。将计算的速率与计算的质量分数耦合,研究了恒星物质轻子到重子分数的时间变化率。我们将我们的结果与文献中报道的先前计算进行比较。与以前的计算报告的显著差异高达数量级。这些差异可能会影响恒星在前超新星后期的演化。我们列出了前50个\textit{ec}和\textit{bd}原子核,这些原子核在硅芯燃烧后的条件下对$Y_e$的影响最大。研究了恒星核中\textit{ec}和\textit{bd}速率之间的竞争,发现$Y_e$ = 0.424- 0.455是\textit{bd}结果大于\textit{ec}速率的区间。

英文摘要:

The project aims to investigate most important weak interaction nuclei in the presupernova evolution of massive stars. To achieve the goal, an ensemble containing 728 nuclei in the mass range A = 1--100 was considered. We computed the mass fractions of these nuclei using Saha's equation for predetermined values of \textit{$T$}, \textit{$ρ$} and \textit{$Y_e$} and assuming nuclear statistical equilibrium. The nuclear partition functions were obtained using a newly introduced recipe where excited states, up to 10 $MeV$, were treated as discrete. The weak interaction rates (electron capture (\textit{ec}) and $β$-decay (\textit{bd})) were calculated in a \textit{totally} microscopic fashion using the proton-neutron quasiparticle random phase approximation (pn-QRPA) model and without assuming the Brink-Axel hypothesis. The calculated rates were coupled with the computed mass fractions to investigate the time rate of change of lepton to baryon fraction of the stellar matter. We compare our results with the previous calculations reported in the literature. Noticeable differences up to orders of magnitude are reported with previous calculations. These differences may influence the evolution of the star in the later stages of presupernova. We present a list of top 50 \textit{ec} and \textit{bd} nuclei which have the largest effect on $Y_e$ for conditions after silicon core burning. The competition between the \textit{ec} and \textit{bd} rates in stellar core was investigated and it was found that $Y_e$ = 0.424--0.455 is the interval where the \textit{bd} results are bigger than the \textit{ec} rates.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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