GW170817: Optical/Infrared Counterpart and Implications for Nucleosynthesis

Abstract

GW170817, the first gravitational wave source from a neutron star merger, has also been observed by electromagnetic waves over a wide wavelength range. This marked the dawn of “multi-messenger” astronomy by the synergy of gravitational waves and electromagnetic waves. Neutron star mergers have been expected to synthesize elements heavier than iron, and emit optical/infrared signals by radioactive decays of newly synthesized elements. Therefore, optical/infrared observations of the counterpart of GW170817 provided unique information about nucleosynthesis in the neutron star merger. In this article, I review what we learned about nucleosynthesis in neutron star mergers and the origin of heavy elements in the Universe through the multi-messenger observations of GW170817.