Frequency of Close Companions among Kepler Planets - a TTV study

TL;DR

This study analyzes over 2600 Kepler planet candidates and finds that systems with more transiting planets have significantly higher fractions of sinusoidal TTVs, suggesting at least two distinct classes of planetary systems.

Contribution

It provides the first large-scale statistical analysis linking TTV fractions to transit multiplicity, revealing a potential dichotomy in Kepler system architectures.

Findings

Higher TTV fractions in multi-planet systems

Approximately five times higher TTVs in systems with four or more planets

Indication of two distinct classes of Kepler planetary systems

Abstract

A transiting planet exhibits sinusoidal transit-time-variations (TTVs) if perturbed by a companion near a mean-motion-resonance (MMR). We search for sinusoidal TTVs in more than 2600 Kepler candidates, using the publicly available Kepler light-curves (Q0-Q12). We find that the TTV fractions rise strikingly with the transit multiplicity. Systems where four or more planets transit enjoy roughly five times higher TTV fraction than those where a single planet transits, and about twice higher than those for doubles and triples. In contrast, models in which all transiting planets arise from similar dynamical configurations predict comparable TTV fractions among these different systems. One simple explanation for our results is that there are at least two different classes of Kepler systems, one closely packed and one more sparsely populated.