Program: GS-2019A-Q-124

Short-duration gamma-ray bursts (SGRBs) are a relativistic class of explosions that are pinpointed to host galaxies via the detection of their faint and rapidly-fading optical afterglows. The most favored progenitors of SGRBs are NS-NS/NS-BH mergers, which are now proven sources of gravitational wave emission and sites of heavy element production in the universe. The precise localization of SGRBs thus offers a unique and complementary way to make progress in neutron star merger studies in the era of GW discovery. Here, we propose to use rapid TOO observations with Gemini to identify the afterglows of SGRBs, and perform spectroscopy at the explosion site of one bright (r<22 mag) event to determine the burst redshift and properties of the burst environment. Following the successful identification of a SGRB at z<0.3, our proposal includes a search for the signature of heavy element production (a NIR "kilonova"), which will place vital constraints on properties of the neutron star merger ejecta. This search will also inform the luminosities and colors of kilonovae, critical and complementary to searches following gravitational wave events detected with Advanced LIGO/Virgo. We focus our proposal on high-impact frontiers in SGRB science that are well-matched to the capabilities of Gemini.