# Merger and Mass Ejection of Neutron-Star Binaries

## TL;DR

This paper reviews recent numerical relativity simulations of neutron star mergers, highlighting their role in predicting gravitational waves, mass ejection, and electromagnetic signals, and compares these predictions with observations like GW170817.

## Contribution

It provides a comprehensive summary of the latest simulation results and their agreement with observational data, advancing understanding of neutron star merger phenomena.

## Key findings

- Numerical relativity simulations broadly agree with GW170817 observations.
- Simulations predict significant mass ejection and electromagnetic counterparts.
- Neutron star mergers are confirmed as key sites for r-process nucleosynthesis.

## Abstract

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.