The period ratio distribution of Kepler's candidate multiplanet systems

TL;DR

This paper analyzes the distribution of orbital period ratios in Kepler's candidate multiplanet systems, revealing features near resonances and a power-law trend, with implications for planetary system formation and evolution.

Contribution

It provides a comprehensive analysis of period ratio distributions, including bias corrections and the discovery of a significant excess near 2.2, advancing understanding of planetary system dynamics.

Findings

Significant excess of planet pairs near period ratio 2.2

Distribution of all period ratios follows a power-law with exponent -1.26

Features observed near first-order mean-motion resonances

Abstract

We calculate and analyze the distribution of period ratios observed in systems of Kepler exoplanet candidates including studies of both adjacent planet pairs and all planet pairs. These distributions account for both the geometrical bias against detecting more distant planets and the effects of incompleteness due to planets missed by the data reduction pipeline. In addition to some of the known features near first-order mean-motion resonances (MMR), there is a significant excess of planet pairs with period ratios near 2.2. The statistical significance of this feature is assessed using Monte Carlo simulation. We also investigate the distribution of period ratios near first-order MMR and compare different quantities used to measure this distribution. We find that beyond period ratios of ~2.5, the distribution of all period ratios follows a power-law with an exponent -1.26 +/- 0.05. We discuss implications that these results may have on the formation and dynamical evolution of Kepler-like planetary systems---systems of sub-Neptune/super-Earth planets with relatively short orbital periods.