A high mutual inclination system around KOI-134 revealed by transit timing variations

TL;DR

This study reveals a non-coplanar planetary system around KOI-134 with high mutual inclination and significant transit timing variations, indicating complex dynamical interactions and challenging existing formation models.

Contribution

First detection of a high mutual inclination in a planetary system via TTVs and TDVs, demonstrating the presence of a non-transiting companion in resonance with a transiting planet.

Findings

KOI-134 b exhibits large TTVs (~20 hours) and TDVs.

A non-transiting planet in 2:1 resonance explains the signals.

KOI-134 c has a mass of approximately 0.22 Jupiter masses and a mutual inclination of about 15.4 degrees.

Abstract

Few planetary systems have measured mutual inclinations, and even less are found to be non-coplanar. Observing the gravitational interactions between exoplanets is an effective tool to detect non-transiting companions to transiting planets. Evidence of these interactions can manifest in the light curve through transit timing variations (TTVs) and transit duration variations (TDVs). Through analysis of Kepler photometry and joint TTV-TDV modeling, we confirm the detection of KOI-134 b, a transiting planet with mass and size similar to Jupiter on a period of ~67 days, and find that it exhibits high TTVs (~20-hr amplitude) and significant TDVs. We explain these signals with the presence of an innermost non-transiting planet in 2:1 resonance with KOI-134 b. KOI-134 c has a mass $M = 0.220^{+0.010}_{-0.011} M_\text{Jup}$ and a moderately-high mutual inclination with KOI-134 b of $i_\text{mut} = 15.4_{-2.5}^{+2.8}{^\circ}$. Moreover, the inclination variations of KOI-134 b are so large that the planet is predicted to stop transiting in about 100 years. This system architecture cannot be easily explained by any one formation mechanism, with other dynamical effects needed to excite the planets' mutual inclination while still preserving their resonance.