Mergers of binary neutron stars and black hole-neutron star binaries are one of the most promising sources for the ground-based gravitational-wave (GW) detectors and also a high-energy astrophysical phenomenon as illustrated by the observations of gravitational waves and electromagnetic (EM) waves in the event of GW170817. Mergers of these neutron-star binaries are also the most promising site for r-process nucleosynthesis. Numerical simulation in full general relativity (numerical relativity) is a unique approach to the theoretical prediction of the merger process, GWs emitted, mass ejection process, and resulting EM emission. We summarize our current understanding for the processes of neutron star mergers and subsequent mass ejection based on the results of the latest numerical-relativity simulations. We emphasize that the predictions of the numerical-relativity simulations agrees broadly with the optical and infrared observations of GW170817.

中文翻译：

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中子星双星的合并和质量抛射

双中子星和黑洞-中子星双星的合并是地基引力波（GW）探测器最有希望的来源之一，也是一种高能天体物理现象，如引力波和电磁波的观测所示（ EM）在 GW170817 事件中的波。这些中子星双星的合并也是 r 过程核合成最有希望的地点。完全广义相对论（数值相对论）中的数值模拟是对合并过程、引力波发射、质量抛射过程和由此产生的电磁发射进行理论预测的独特方法。我们根据最新的数值相对论模拟结果总结了我们目前对中子星合并和随后的质量抛射过程的理解。