Program: GS-2018A-Q-205

We propose to continue our rapid-response target of opportunity (ToO) program to study the nature and origin of fast radio bursts (FRBs). Analogous to the gamma-ray bursts (GRBs), the FRBs are an enigmatic class of transient sources discovered outside the optical/near-IR passbands. Their radio emission, however, offers limited insight into their physical nature and, especially, cannot be used to precisely establish the source redshift. We propose to perform follow-up observations of real time well-localized FRB alerts, in order to characterize any putative optical counterpart and/or the host galaxy, and then use Gemini-S to trigger a rapid response imaging or spectroscopic observations using GMOS. Our science goals range from establishing the energetics and progenitors of the FRBs to leveraging these phenomena for cosmological constraints on the distribution of baryons within the intergalactic medium and other applications.