Architecture and Dynamics of Kepler's Candidate Multiple Transiting Planet Systems

TL;DR

This study analyzes the architecture and dynamics of Kepler's multi-planet candidate systems, revealing their stability, resonance patterns, and inclination distributions, and inferring their true multiplicity and planetary nature.

Contribution

It provides the first detailed characterization of the dynamical properties and true multiplicity of Kepler's multi-planet candidate systems, including resonance excesses and inclination constraints.

Findings

Most candidate pairs are not in low-order resonances.

Virtually all candidate systems are dynamically stable.

The systems likely contain multiple low-inclination super-Earth and Neptune-sized planets.

Abstract

About one-third of the ~1200 transiting planet candidates detected in the first four months of \ik data are members of multiple candidate systems. There are 115 target stars with two candidate transiting planets, 45 with three, 8 with four, and one each with five and six. We characterize the dynamical properties of these candidate multi-planet systems. The distribution of observed period ratios shows that the vast majority of candidate pairs are neither in nor near low-order mean motion resonances. Nonetheless, there are small but statistically significant excesses of candidate pairs both in resonance and spaced slightly too far apart to be in resonance, particularly near the 2:1 resonance. We find that virtually all candidate systems are stable, as tested by numerical integrations that assume a nominal mass-radius relationship. Several considerations strongly suggest that the vast majority of these multi-candidate systems are true planetary systems. Using the observed multiplicity frequencies, we find that a single population of planetary systems that matches the higher multiplicities underpredicts the number of singly-transiting systems. We provide constraints on the true multiplicity and mutual inclination distribution of the multi-candidate systems, revealing a population of systems with multiple super-Earth-size and Neptune-size planets with low to moderate mutual inclinations.