UC Santa Barbara

The most extreme phenomena in the universe present the most intriguing opportunities to test our understanding of physics in environments no laboratory on Earth can simulate. In this dissertation, I present a series of observational and theoretical studies of extreme astrophysical systems, spanning infant supernovae and horizon-scale black hole physics. First, I investigate the earliest phases of core-collapse supernovae in both optical and radio wavelengths, describing and applying a framework for the robust application of shock-cooling models across the hydrogen-rich envelope mass spectrum. Next, I consider theoretical properties of the black hole shadow in general relativity, and extend these to perform angular momentum inference using modern very-long-baseline interferometers in dynamically evolving horizon-scale systems. These results directly contribute to the second Event Horizon Telescope image of a black hole (the first image of Sagittarius A*) and help explore the science case for the future Black Hole Explorer mission. Finally, this dissertation bridges the domains of supernovae astrophysics and general relativity by identifying and characterizing the first supernova to show evidence of a relativistic frame-dragging central engine in its light curve, providing observational confirmation of the magnetar model for superluminous supernovae.