In Pursuit of New Worlds: Searches for and Studies of Transiting Exoplanets from Three Space-Based Observatories

Abstract

This thesis presents studies of transiting exoplanets using observations gathered in large part from space, with the NASA EPOXI Mission, the Spitzer Space Telescope, and the Kepler Mission. The first part of this thesis describes searches for additional transiting planets in known exoplanet systems, using time series photometry gathered as part of the NASA EPOXI Mission. Using the EPOXI light curves spanning weeks for each star, we searched six exoplanetary systems for signatures of additional transiting planets. These six systems include five hosts to hot Jupiters: HAT-P-4, TrES-3, TrES-2, WASP-3, and HAT-P-7, and one host to a hot Neptune: GJ 436. We place upper limits on the presence of additional transiting planets in the super-Earth radius range for GJ 436 in Chapter 2, and in the Neptune-to-Saturn radius range for the other five systems in Chapter 4. Chapter 3 details a search for additional transits of a hypothesized planet smaller than the Earth, whose presence was suggested by the EPOXI observations of GJ 436. In that study, we demonstrate the sensitivity of Warm Spitzer observations to transits of a sub-Earth-sized planet. The fifth chapter details the characterization and validation of the Kepler-19 system, which hosts a transiting 2.2 (R_{\bigoplus}) planet, Kepler-19b. We demonstrate the planetary nature of the transit signal with an analysis that combines information from high-resolution spectroscopy, the shape of the transit light curve, adaptive optics imaging, and near-infrared transits of the planet. The sinusoidal variation in the transit times of Kepler-19b indicates the presence of an additional perturbing body, and comprises the first definitive detection of a planet using the transit timing variation method. While we cannot uniquely determine the mass and orbital period of Kepler-19c, we establish that its mass must be less than 6 times the mass of Jupiter. The sixth chapter presents evidence for the validation of a 2.0 (R_{\bigoplus}) planet residing in the habitable zone of a low-mass star, Kepler Object of Interest 1361.01. We discuss the theoretical composition of the planet, and address issues specific to habitability of planets orbiting M dwarfs.