Shedding light on hostless short GRBs with large aperture telescopes

Short gamma-ray bursts (sGRBs) are bright flashes of gamma-rays lasting for less than 2 seconds. These events were unambiguously connected to binary neutron star mergers by the simultaneous detection of GW170817 and GRB 170817A. Therefore, sGRBs play a significant role in modern astrophysics with far-reaching implications from the rate of detectable gravitational wave events from compact binary mergers to the production of heavy elements in the universe. Their environments and distance scales yield important information as to their progenitors and their formation channels. However, a significant fraction of sGRBs lack a coincident host galaxy to deep limits (r\geq26 AB mag) and are found significantly offset from any other potential host galaxy. These highly offset events are a direct prediction of the compact binary merger model, and their rate improves our understanding of the formation and evolution of compact binaries, complementing the constraints derived from gravitational wave astronomy. For this reason, we began a systematic search for these events by targeting all sGRBs without a known host galaxy association. Here, we present the results of our observing campaign, including deep Gemini, Keck and HST imaging of 31 new short GRBs. Our study effectively doubles the sample of well studied sGRB galaxies and represents the largest catalog to date of sGRB offsets