First Multimessenger Observations of a Neutron Star Merger

Understand

We describe the first observations of the same celestial object with gravitational waves and light.

• * GW170817 was the first detection of a neutron star merger with gravitational waves.
• * The detection of a spatially coincident weak burst of $\gamma$-rays (GRB 170817A) 1.7 s after the merger constituted the first electromagnetic detection of a gravitational wave source and established a connection between at least some cosmic short gamma-ray bursts (SGRBs) and binary neutron star mergers.
• * A fast-evolving optical and near-infrared transient (AT 2017gfo) associated with the event can be interpreted as resulting from the ejection of $\sim$0.05 M$_{\odot}$ of material enriched in r-process elements, finally establishing binary neutron star mergers as at least one source of r-process nucleosynthesis.