Multiwavelength studies of gravitational wave sources: Physics and phenomenology

The discovery of binary neutron star merger GW170817 from its gravitational wave signature, together with its accompanying electromagnetic emission spanning gamma-ray to radio, marked the birth of GW+EM multi-messenger astrophysics. The radioactively-powered thermal kilonova, which dominated the ultraviolet to infrared in the hours to weeks after the merger, indicates that such mergers are the site of heavy element nucleosynthesis, likely extending to the third r-process peak.

The prompt gamma-ray flash, and late time non-thermal (X-ray to radio) emission, indicate that the merger also produced an ultra-relativistic jet, thus tying this event to the phenomena of short-duration gamma-ray bursts. In the future, observations of further mergers promise to establish their contribution to global nucleosynthesis, allow investigation of jet launching and structure, provide independent estimates of the cosmological parameters, constrain the neutron star equation of state, and address questions of fundamental physics.