The Frontier of Cosmic Cataclysms
Creators: name: Ridden-Harper, Ryan
Publisher: name: The Australian National University
Year: 2020

description: The short time domain (≤ 1 day) is the frontier of transient astronomy. In this frontier, new phenomena are waiting to be discovered that may hold the answers to crucial questions, particularly for progenitors of extreme events e.g., supernovae, gravitational waves/kilonovae, and gamma-ray bursts. Telescope systems across the world, such as Pan-STARRS, ASAS-SN, ATLAS, and ZTF are pushing towards shorter cadences, however, they are still limited by the diurnal cycle and weather. Although these telescope systems are successful at discovering transients that evolve over many days, such as supernovae, they are currently unable to systematically explore the very rapid time domain of transients and features that evolve on time scales ≤ 1 day. In this thesis we seek to explore the short time domain to discover and understand short phenomena. To begin this exploration, we consider two pathways into the frontier of rapid transients: a high altitude balloon borne ultra-violet survey telescope, known as GLUV, optimised to detect type Ia supernova shock interactions and core collapse supernovae shock breakouts; and we developed the Background Survey, to conduct a systematic a transient survey of high cadence data obtained by the Kepler Space Telescope (Kepler ). With these two pathways, we were able to actively explore the short time domain, while developing a purpose built instrument. We find that for GLUV to routinely detect SN Ia shock interactions, it must have a limiting magnitude of ∼ 21. GLUV could meet this sensitivity if it features a 30 cm primary mirror, allowing it to determine the progenitor systems responsible for cosmological SN Ia. The same telescope design would also provide valuable diagnostic information on counterparts of gravitational wave events, such as kilonovae and possible emission from binary black hole mergers. Through the Kepler/K2 Background Survey, we find that there are still transients to be discovered in the Kepler/K2 data. In initial tests, we discover a new WZ Sagittae type dwarf nova, named KSN:BS-C11a. Through the superb high cadence photometry afforded by Kepler, we are able to constrain a number of physical properties of the system, and discover that the rise of dwarf novae superoutbursts can be characterised by a broken power law. The presence of the broken rise suggests new physics in how the superoutbursts begins. We also observe the broken rise phenomena in another dwarf nova discovered and observed by Kepler and Z Chamaeleontis, which was observed by TESS. The discovery of KSN:BS-C11a and its subsequent properties was only possible through high-cadence observations, and is indicative of future discoveries that can be made in the short time domain frontier. The short time domain of transient astronomy offers the potential for many new and novel discoveries. Many of these discoveries will come from the unique high cadence data obtained by Kepler and by TESS, of which the Background Survey is the best tool to make these discoveries. As we learn more about the short time domain, dedicated transient telescope systems such as GLUV will be poised to make full use of the advancing knowledge, as we explore the new frontier of astronomy.