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arXiv 2010.01698nucl-thastro-ph.SR
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Hauser-Feshbach不确定性估计对r-过程核合成的传播：远离稳定的丰中子核统计性质模型的基准

Propagation of Hauser-Feshbach uncertainty estimates to r-process nucleosynthesis: Benchmark of statistical property models for neutron rich nuclei far from stability

S. Nikas, G. Perdikakis, M. Beard, R. Surman, M. R. Mumpower, P. Tsintari

备注：
Submitted to Phys. Rev. C (abstract adapted to arXiV character limit and style)
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摘要：

对中子星合并事件GW 170817的多信使观测重新激发了关于大质量元素通过r过程核合成的天体物理起源的争论。这种研究的一个关键方面是以一种有意义的方式将天文观测与理论核合成产量进行比较。为了进行真实的核合成计算，理解微观物理细节（如核反应速率）的不确定性与理解天体物理环境建模中的不确定性一样重要。我们提出了一个调查的中子俘获率计算的不确定性远离稳定使用豪泽-Feshbach模型。我们提供了一个定量测量的计算的可靠性时，我们外推模型的统计性质的核在r-过程网络。我们选择了几个适合于中子俘获的能级密度和γ射线强度模型，并用它们来计算网络中每个核的反应速率。我们观察统计特性如何影响理论反应速率。然后用蒙特卡罗技术对速率进行采样，并用于网络计算，以绘制可能的r-过程丰度的范围。结果表明，计算之间的中子捕获率可以变化几个数量级。现象学模型提供比半微观更平滑的结果。然而，它们不能再现原子核结构的变化，如壳的闭合。虽然半微观模型预测原子核结构效应远离稳定性，但尚不清楚这些结果在定量上是否准确。不确定性对r-过程产率的影响大到足以阻碍观测和计算之间的比较。发展更好的微观模型的伽马强度和能级密度的进展是迫切需要提高r-过程模型的保真度。

英文摘要：

Multimessenger observations of the neutron star merger event GW170817 have re-energized the debate over the astrophysical origins of the most massive elements via the r-process nucleosynthesis. A key aspect of such studies is comparing astronomical observations to theoretical nucleosynthesis yields in a meaningful way. To perform realistic nucleosynthesis calculations, understanding the uncertainty in microphysics details such as nuclear reaction rates is as essential as understanding uncertainties in modeling the astrophysical environment. We present an investigation of neutron capture rate calculations' uncertainty away from stability using the Hauser-Feshbach model. We provide a quantitative measure of the calculations' dependability when we extrapolate models of statistical properties to nuclei in an r-process network. We select several level density and gamma-ray strength models appropriate for neutron-capture and use them to calculate the reaction rate for each nucleus in the network. We observe how statistical properties affect the theoretical reaction rates. The rates are then sampled with the Monte Carlo technique and used in network calculations to map the range of possible r-process abundances. The results show that neutron capture rates can vary by a couple of orders of magnitude between calculations. Phenomenological models provide smoother results than semi-microscopic. They cannot, however, reproduce nuclear structure changes such as shell closures. While semi-microscopic models predict nuclear structure effects away from stability, it is not clear that these results are quantitatively accurate. The effect of the uncertainty on r-process yields is large enough to impede comparisons between observation and calculations. Progress in developing better microscopic models of gamma strengths and level densities is urgently needed to improve the fidelity of r-process models.

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