UC Berkeley

The liberation of gas from a star's outer layers (i.e., mass loss) is a fundamental part of its evolution from stellar conception to demise. However, given that most of the resolved, local stars in the Universe will not explode on a human timescale, alternate probes of late-stage stellar evolution are required to quantify the mass-loss rates of stars in their final years, decades, and centuries. One such method is observing the collision between ejected stellar material in a supernova (SN) and pre-existing circumstellar material (CSM), the latter being formed from stellar activity (e.g., steady winds, turbulent eruptions, and/or binary interaction) prior to the terminal explosion, which produces the former. In this thesis, I demonstrate how early-time (~days post-explosion), multi-wavelength observations of CSM-interacting supernovae can be synthesized to directly constrain both progenitor identity and mass-loss history during the final stages of stellar evolution for a variety of SN subtypes, both from massive and compact stars.