Program: GN-2019B-Q-130

The discovery of an electromagnetic counterpart to the first binary neutron star merger detected via gravitational waves (GW170817) heralds a new era in multi-messenger astronomy. The only two wave-bands where the emission is ubiquitous, independent of viewing angle, mass ratio and remnant lifetime, are the infrared and the radio. The infrared may even be the only way to pinpoint the merger of a neutron star with a black hole, as they are predicted to be optically dark. Furthermore, due to the high opacity, the infrared is essential to study heavy element (r-process) nucleosynthesis. Here, we propose to leverage Gemini's unique queue-scheduling capabilities and near-infrared sensitivity to localize and characterize the electromagnetic counterparts of neutron star mergers. Our experience with GW170817 demonstrates the effectiveness of combining a galaxy catalog with LIGO/Virgo localizations in order to leverage 8m class telescopes as an initial discovery engine. And with detailed NIR spectroscopic follow-up of multiple compact binary mergers in O3, we will conduct a census of heavy element formation to determine if binary neutron star mergers can indeed reproduce Solar r-process abundances.