Probing Relativistic Jets with Radio Observations: The Case Study of GW170817
With the advent of sensitive facilities like the Karl G. Jansky Very Large Array (VLA) and planning well underway for vastly more powerful wide-field interferometers like the Square Kilometer Array, the study of radio astrophysical transients is poised for dramatic growth. Radio observations provide a unique window into a wide variety of astrophysical transients, from gamma-ray bursts to tidal disruptions of stars by supermassive black holes. In these high-energy laboratories, the longer timescale of radio emission allows for extensive followup, probing the physics underlying the formation and growth of relativistic jets and outflows. I will present radio observations of GW170817, the first binary neutron star merger observed in gravitational waves. Our full multi-wavelength dataset (Alexander et al. 2018) is consistent with a successful structured jet expanding into a low-density circumbinary medium. Future events will shed light on the question of whether all binary neutron star mergers produce successful relativistic jets.