恒星物质中由$^{56}$ Ni引起的弱相互作用介导的中微子冷却速率的扩展计算
Expanded calculation of weak-interaction mediated neutrino cooling rates due to $^{56}$Ni in stellar matter
摘要：
为了研究大质量恒星恒星演化的各个阶段，需要精确地估计中微子冷却速率。原中子星的中微子损失在决定这些恒星是否会被压碎成黑洞或爆炸成超新星方面起着至关重要的作用。纯轻子过程和弱相互作用过程都对中微子在恒星物质中的能量损失有贡献。在低温度和低密度下，作为前超新星演化的早期阶段的特征，通过由弱相互作用产生的中微子冷却是重要的。质子-中子准粒子无规相近似（pn-QRPA）理论最近被成功地用于计算$fp$壳层核素的恒星弱相互作用率。在大质量恒星演化的早期阶段，轻子-重子比（$Y_{e}$）的变化主要是由于电子在$^{56}$ Ni上的俘获。恒星物质对大质量恒星超新星前演化过程中产生的中微子是透明的。这些中微子逃离了这个位置，帮助恒星核心保持较低的熵。本文用pn-QRPA理论对恒星物质中$^{56}$ Ni引起的弱相互作用介导的中微子和反中微子冷却速率进行了扩展计算。这种详细的比例尺适用于插值目的，并且对于仿真代码具有更大的实用性。将计算出的比率与先前的计算进行比较。在恒星物质的相关温度和密度区域，所报道的速率与壳层模型的速率差别不大，可能有助于大质量恒星恒星演化的前超新星阶段轻子-重子比的微调。
英文摘要：
Accurate estimate of the neutrino cooling rates is required in order to study the various stages of stellar evolution of massive stars. Neutrino losses from proto-neutron stars play a crucial role in deciding whether these stars would be crushed into black holes or explode as supernovae. Both pure leptonic and weak-interaction processes contribute to the neutrino energy losses in stellar matter. At low temperatures and densities, characteristic of the early phase of presupernova evolution, cooling through neutrinos produced via the weak-interaction is important. Proton-neutron quasi-particle random phase approximation (pn-QRPA) theory has recently being used for calculation of stellar weak-interaction rates of $fp$-shell nuclide with success. The lepton-to-baryon ratio ($Y_{e}$) during early phases of stellar evolution of massive stars changes substantially alone due to electron captures on $^{56}$Ni. The stellar matter is transparent to the neutrinos produced during the presupernova evolution of massive stars. These neutrinos escape the site and assist the stellar core in maintaining a lower entropy. Here I present the expanded calculation of weak-interaction mediated neutrino and antineutrino cooling rates due to $^{56}$Ni in stellar matter using the pn-QRPA theory. This detailed scale is appropriate for interpolation purposes and of greater utility for simulation codes. The calculated rates are compared against earlier calculations. During the relevant temperature and density regions of stellar matter the reported rates show little differences with the shell model rates and might contribute in fine-tuning of the lepton-to-baryon ratio during the presupernova phases of stellar evolution of massive stars.
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