Time-Domain Astrophysics with the Transiting Exoplanet Survey Satellite

Abstract

The Transiting Exoplanet Survey Satellite (TESS) is conducting an all-sky survey with the primary aim of detecting planets orbiting nearby stars. However, its large field of view and 200 s imaging cadence are useful for other science cases, ranging from stellar astrophysics to transient science. This thesis focuses on using TESS to study both the circumstellar environment and stellar interiors, as well as using the satellite to detect and characterize optical emission from gamma-ray bursts (GRBs). Chapter 2 focuses on the discovery of HD 135348, a "rigidly rotating magnetospheric" star–wherein the stellar magnetic field traps dust in a co-rotating orbit and leads to complex periodic photometric modulations–using solely photometric data. Chapter 3 focuses on the discovery of a long-period subdwarf B (sdB) star using 20 s cadence TESS data and proposes a novel formation mechanism for long-period sdB stars that relies upon stable, nonconservative mass transfer. Chapters 4 and 5 focus on pulsating stars in close binaries, and the evolutionary insights that these "tidally tilted" pulsations enable. In particular, we focus on developing models to track the amplitude and phase of these pulsations as a function of orbital phase, as well as tools to perform physically-motivated modeling of the binary components. Chapters 6-7 focus on the optical signatures of gamma-ray bursts in TESS, and analyze the prompt optical flash that is often observed contemporaneously with the high-energy emission from these bursts. Chapter 7, in particular, aims to connect the prompt optical flash to the high-energy spectral energy distribution (SED), and explains the suppression of the optical flash (compared to the extrapolation of the high-energy SED) by invoking dust extinction in the host galaxy. This thesis represents a significant step forward in both stellar and transient astrophysics; throughout this work, we emphasize the use of an unconventional tool–TESS–to pursue timely scientific questions.