研究双中子星并合中带电流过程全运动学处理的影响

中文摘要 AI 辅助

弱相互作用在双中子星（BNS）并合中至关重要。它们提供冷却、改变物质外流的组成，并可通过中微子驱动风导致显著的长期外流。因此，在中子星并合的数值相对论模拟中，包含中微子输运已成为标准做法。更详细地说，在截断的二阶矩方案（M1）中，中微子与物质的相互作用通过相互作用率来描述，这些相互作用率由一组标准相互作用计算得出。其中包括带电流反应，通常假设这些反应采用弹性近似。更复杂的替代方案包括公开可用的NuLib库，或在全运动学方法中计算的速率。在本工作中，我们比较了使用这三种计算带电流弱作用率方案的BNS系统并合模拟，这些方案被纳入带有隐式-显式时间积分器的M1方程中。我们发现，弹性近似略微高估了动力学抛射质量，同时低估了其中高电子丰度物质的含量。此外，它在早期高估了中微子光度。与NuLib速率相比，全运动学的影响在模拟数据的不确定性范围内似乎可忽略不计。类似地，对于三种方案，并合后的引力波谱在数值不确定性内无法区分。使用核网络计算的核合成产额大体一致，但在原子质量范围$A\in[90,125]$内，弹性近似显示出更大的丰度。最后，不同的相互作用率似乎影响残余盘的性质，这暗示了更准确的相互作用率对于跨越长期时间尺度的模拟的重要性。

英文摘要

Weak interactions are fundamental in the merger of binary neutron stars (BNS). They provide cooling, change the composition of matter outflows, and can lead to significant secular outflows through neutrino-driven winds. Hence, the inclusion of neutrino transport has become standard in numerical-relativity simulations of mergers involving neutron stars. In more detail, the interactions of neutrinos with matter in a truncated two-moments scheme (M1) are described through interaction rates, calculated from a set of standard interactions. Among those are charged-current reactions, for which the elastic approximation is commonly assumed. More sophisticated alternatives are provided by, e.g., the publicly available NuLib library, or rates computed within a full kinematics approach. In this work, we compare merger simulations of a BNS systems employing each of these three prescriptions for the computation of charged-current weak rates, included in the M1 equations with an implicit-explicit time integrator. We find that the elastic approximation slightly overestimates the dynamical ejecta mass, while underestimating the amount of high electron fraction material therein. Additionally, it overestimates the neutrino luminosities at early times. The effects of full kinematics in comparison to the NuLib rates appear negligible within the uncertainties of the simulation data. Similarly, the post-merger gravitational-wave spectra for the three prescriptions were found to be indistinguishable within the numerical uncertainties. Nucleosynthetic yields, computed with a nuclear network, are broadly consistent, except in the atomic mass range $A\in[90,125]$ where the elastic approximation shows larger abundances. Finally, the different interaction rates seem to affect the remnant disk properties, hinting at the importance of more accurate interaction rates for simulations spanning secular timescales.

发表机构

• Institut für Physik und Astronomie, Universität Potsdam（波茨坦大学物理与天文学研究所）

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