Wang Long-Jun, Tan Liang, Li Zhipan, Misch G Wendell, Sun Yang
School of Physical Science and Technology, Southwest University, Chongqing 400715, China.
Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
Phys Rev Lett. 2021 Oct 22;127(17):172702. doi: 10.1103/PhysRevLett.127.172702.
The excited-state structure of atomic nuclei can modify nuclear processes in stellar environments. In this Letter, we study the influence of nuclear excitations on Urca cooling (repeated back-and-forth β decay and electron capture in a pair of nuclear isotopes) in the crust and ocean of neutron stars. We provide for the first time an expression for Urca process neutrino luminosity which accounts for a thermal Boltzmann distribution of excited states in both members of an Urca pair. We use our new formula with state-of-the-art nuclear structure inputs to compute neutrino luminosities of candidate Urca cooling pairs. Our nuclear inputs consist of the latest experimental data supplemented with calculations using the projected shell model. We show that, in contrast to previous results that only consider the ground states of both nuclei in the pair, our calculated neutrino luminosities for different Urca pairs vary sensitively with the environment temperature and can be radically different from those obtained in the one-transition approximation. We find that nuclear excitations can lead to an enhancement in total Urca neutrino luminosities in the accreted neutron star crust by about 5 times as compared with the previous Urca results, which is expected to cause significant observational effects.
原子核的激发态能够改变恒星环境中的核过程。在本信函中，我们研究了核激发对中子星地壳和海洋中乌卡冷却过程（一对核同位素中反复的来回β衰变和电子俘获）的影响。我们首次给出了乌卡过程中微子光度的表达式，该表达式考虑了乌卡对中两个成员激发态的热玻尔兹曼分布。我们使用具有最先进核结构输入的新公式来计算候选乌卡冷却对的中微子光度。我们的核输入由最新的实验数据以及使用投影壳模型的计算结果补充而成。我们表明，与之前仅考虑对中两个原子核基态的结果不同，我们计算得到的不同乌卡对的中微子光度随环境温度敏感变化，并且可能与单跃迁近似下得到的结果有根本差异。我们发现，与之前的乌卡结果相比，核激发可使吸积中子星地壳中的总乌卡中微子光度增强约5倍，这预计会产生显著的观测效应。
