AbstractsAstronomy & Space Science

Over the past 20 years, we have learned that exoplanets are ubiquitous throughout our Galaxy and show a diverse set of demographics, yet there is much work to be done to understand this diversity. Determining the distributions of the fundamental properties of exoplanets will provide vital clues regarding their formation and evolution. This is a difficult task, as exoplanet surveys are not uniformly sensitive to the full range of planet parameter space. Various observational biases and selection effects intrinsic to each of the different discovery techniques constrain the types of planets to which they are sensitive. Herein, I record a collection of the first studies to develop and apply the methodology of synthesizing results from multiple detection techniques to construct a statistically-complete census of planetary companions to M dwarfs that samples a wide region of their parameter space. I present a robust comparison of exoplanet discoveries from microlensing and radial velocity (RV) surveys of M dwarfs which infer giant planet frequencies that differ by more than an order of magnitude and are, prima facie, in direct conflict. I demonstrate that current, state-of-the-art RV surveys are capable of detecting only the high-mass tail of the population of planets beyond the ice line inferred by microlensing studies, engendering a large, apparent difference in giant planet frequency. This comparison further establishes that results from these types of surveys are, in fact, consistent over the region of parameter space wherein their sensitivities overlap. A synthesis of results from microlensing and RV surveys yields planet occurrence rates for M dwarfs that span several orders of magnitude in mass and orbital period. On average, each M dwarf hosts about two planets, and while Jupiter and super-Jupiter companions are relatively rare (~3%), gas giants, in general, are quite common (~15%). These occurrence rates are significantly lower than those inferred around FGK stars and are thus, at least qualitatively, consistent with the predictions of core accretion theory. Finally, I present a synthesis of results from microlensing, RV, and direct imaging surveys that improve constraints on the demographics of long-period, massive planetary companions to M dwarfs. I demonstrate that the results of five different surveys for exoplanets employing these three independent techniques are consistent with a single population of planets described by a simple, joint power-law distribution function in mass and semimajor axis, and provide constraints on the parameters of such a population. The final result is the most statistically-complete census of exoplanets that has hitherto been constructed for a given type of host star, spanning a mass range of 1-104 M¿ and an orbital period range of 1-105 days. This work represents an important benchmark for all future exoplanet population studies, and the methodologies developed herein are applicable to new and larger data sets of forthcoming… Advisors/Committee Members: Gaudi, B. Scott (Advisor).