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 April, advanced
LIGO and VIRGO are in O3 observation and already had a few candidates
of neutron-star mergers. We expect several 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.
