UCLA

Planets are now known to be near ubiquitous around main-sequence stars in our galaxy, as evidenced by the results of radial velocity and transit surveys such as the Kepler mission. In spite of this accomplishment, our understanding of how planetary systems form and are affected by stellar evolution is far from complete. Observations of polluted white dwarfs, which show evidence for planetesimal accretion in their atmospheres, indicate that planets must be orbiting them in order to perturb planetesimals into their tidal radius. Yet no planets have themselves been detected, leaving the population uncharacterized. Meanwhile, main-sequence stars host a significant number of eccentric warm jupiters, massive planets orbiting on 10- to 100-day periods, which are not observed around evolved stars. These planets were likely born at much larger distances, but the mechanism by which they migrated inward remains unclear.

This dissertation is composed of two projects, each investigating one of these populations. In the first I use numerical simulations to test eccentric planets as the source of white dwarf pollution, finding a strong relationship between planetary properties and the white dwarf accretion rate. Small and eccentric planets prove to be the most efficient perturbers, capable of producing the observed pollution levels so long as the surviving disk of planetesimals is massive enough. In the second I test the hypothesis that warm jupiters are migrating as a result of large oscillations in eccentricity caused by a more distant planet. Our numerical simulations show that these oscillations lead to planetary removal earlier in the evolution of the host star than constant eccentricity, and can explain the observed lack of warm jupiters around evolved stars.