Observational constraints on Supernovae and Supernova Impostors

This thesis focuses on the observational campaign for the interacting transient AT 2016jbu, and the development and workings of a novel automated photometry code, AutoPhOT. We provide an overview of the current stellar evolutionary theory and transient astronomy, including a brief section on photometry, in Chapter 1. Chapter 2 covers the Automated Photometry Of Transients (AutoPhOT) photometric pipeline. This software package was designed to provide a fast, precise, and accurate means for the modern astronomer to measure the magnitude of astronomical point sources. We demonstrate the modern photometric techniques implemented in the code, and its capabilities to produce publication ready data with little human interaction. Chapters 3 and 4 cover the observational campaign for the interacting transient, AT 2016jbu. This transient was observed almost a decade before it exploded, allowing for strong constraints on the progenitor. Comparing to the current stellar evolutionary theory, this star is not expected to explode as a core collapse supernova, and one must question whether we are observing the death of a star at all. We present the multi-chromatic dataset for AT 2016jbu in Chapter 3 and compare with similar transients. Chapter 4 focuses on modelling the progenitor for AT 2016jbu and using a high quality, high cadence dataset, we attempt to model the transient, producing a self-consistent explosion model, that may be applied to similar transients. In Chapter 5, we present observations from the Hubble Space Telescope almost 5 years after its apparent demise. The goal of these measurements was to address whether the progenitor may have survived the 2016 events, and is now enshrouded by massive amounts of dust formed in the ejecta of AT 2016jbu. We find a unrealistic amount of dust (for a non-terminal explosion) is needed to hide the progenitor. We conclude that AT 2016jbu is indeed a genuine, albeit strange, terminal explosion and further investigate a possible explosion scenario, focusing on massive stars within a binary system. Chapter 6 provides a general overview of the most salient findings found during this thesis and comments on future work.