Quantifying the Diversity of Relativistic Transients with Radio Observations

Time domain astronomy has grown spectacularly in recent years due to NASA missions like Swift and Fermi and the implementation of untargeted optical surveys like Pan-STARRS, PTF, and ASAS-SN. In particular, they have greatly expanded the sample of rare relativistic transients, from long and short gamma-ray bursts (LGRBs and SGRBs) to tidal disruption events (TDEs) in which a star is torn apart by a supermassive black hole (SMBH). I propose to obtain detailed radio observations of these events to probe the formation of relativistic jets and outflows. Radio provides the best constraints on the fastest-moving ejecta and the surrounding density. The advent of sensitive facilities like the Karl G. Jansky Very Large Array and the Atacama Large Millimeter/submillimeter Array in combination with deep all-sky optical surveys means that for the first time, we can identify and study complete populations of relativistic transients, not just the brightest outliers. The work I propose will place the most extreme events in broader contexts: TDEs in the context of SMBH variability and growth, LGRBs in the context of stellar evolution, and SGRBs in the context of the first unbiased sample of binary neutron star mergers, provided by Advanced LIGO/Virgo.