Institute for Advanced Study/Princeton University Joint Astrophysics Colloquium

On August 17th, 2017, merger of binary neutron stars was observed for the first time by gravitational-wave and electromagnetic telescopes. Optical and infrared observations in particular agree broadly with the prediction by numerical relativity. From this March, advanced LIGO and VIRGO will start observation again and we expect a few more observations of neutron-star mergers (including black hole- neutron star merger). I will review our current understanding for neutron-star mergers and related mass ejection that are obtained by numerical relativity simulations and summarize predicted observational (optical and infrared) features for next events.