A Comprehensive Study of the Kepler Triples via Eclipse Timing

TL;DR

This study analyzes eclipse timing variations in approximately 2600 Kepler binary systems to identify and characterize third-body companions, revealing statistical properties and supporting theories of triple system formation and evolution.

Contribution

The paper introduces new techniques for analyzing ETV curves, reports 222 systems with confirmed third bodies, and provides detailed system parameters for 62 triples, expanding understanding of triple star dynamics.

Findings

Strong evidence for third bodies in 222 systems.

Distribution peak near 40 degrees supports Kozai-Lidov cycles.

Substantial fraction of binaries are in triple systems.

Abstract

We produce and analyze eclipse time variation (ETV) curves for some 2600 Kepler binaries. We find good to excellent evidence for a third body in 222 systems via either the light-travel-time (LTTE) or dynamical effect delays. Approximately half of these systems have been discussed in previous work, while the rest are newly reported here. Via detailed analysis of the ETV curves using high-level analytic approximations, we are able to extract system masses and information about the three-dimensional characteristics of the triple for 62 systems which exhibit both LTTE and dynamical delays; for the remaining 160 systems we give improved LTTE solutions. New techniques of preprocessing the flux time series are applied to eliminate false positive triples and to enhance the ETV curves. The set of triples with outer orbital periods shorter than ~2000 days is now sufficiently numerous for meaningful statistical analysis. We find that (i) as predicted, there is a peak near i_m~40 deg in the distribution of the triple vs. inner binary mutual inclination angles that provides strong confirmation of the operation of Kozai-Lidov cycles with tidal friction; (ii) the median eccentricity of the third-body orbits is e_2=0.35; (iii) there is a deficit of triple systems with binary periods <1 day and outer periods between ~50 and 200 days which might help guide the refinement of theories of the formation and evolution of close binaries; and (iv) the substantial fraction of Kepler binaries which have third-body companions is consistent with a very large fraction of all binaries being part of triples.