Mean Motion Resonances and Planetary Scattering

Sammanfattning: The observed distribution of giant exoplanet eccentricities and inclinations are significantly larger than what is measured for their Solar system analogues, Jupiter and Saturn. Since the first observations of exoplanets, planet-planet scattering has been proposed as a possible mechanism for exciting the eccentricities and inclinations of giant exoplanets. Many works have showed that indeed the observations can be reproduced fairly well by unstable planetary systems undergoing planet-planet scattering, e.g. Marzari & Weidenschilling (2002); Juri´c & Tremaine (2008); Chatterjee et al. (2008). Most of these works disregard mean motion resonances in their simulations. In the early stages of a planet system the planets are embedded in a protoplanetary disk, consisting mostly of gas. Planet-disk interactions causes planets to migrate which allows for capture into mean motion resonances. This significantly affects the dynamical evolution of the system. In this work I investigate what effect mean motion resonances has specifically on the planet-planet scattering phase of an unstable system. I numerically simulate systems of three Jupiter-mass planets orbiting a solar mass star, including planetdisk interactions to form resonant configurations. The systems are split into two sets: mmr simulations, with all planets locked in mean motion resonance chains before the scattering phase, and non-mmr simulations, with similar initial orbital elements but no mean motion resonances before the scattering phase. I find that eccentricity and inclination distributions of relaxed systems are not directly correlated with initial mean motion resonances. Resonances seem to be broken in the first few close encounters and have no further impact on the systems afterwards. However, mean motion resonances have an impact on the initial eccentricity, inclination and semimajor axis of the scattering phase, all of which affects the relaxed systems. Therefore mean motion resonances do affect the scattering phase indirectly through the initial orbital elements. The duration of the scattering phase seems to be uncorrelated with both initial resonance and initial eccentricity and inclination. The onset time of the scattering phase is, in contrast, very dependent on both initial mean motion resonance and initial orbital elements.