The six-planet resonant chain of HD 110067

TL;DR

HD 110067 hosts a likely six-planet resonant chain, with dynamical stability analyses supporting resonance, constraining planetary properties, and predicting transit timing variations, despite limited observational data.

Contribution

This study provides the first strong evidence that all six planets in HD 110067 form a resonant chain, using dynamical stability to infer system architecture and planetary parameters.

Findings

All six planets are likely in a resonant chain.

Nonresonant models are dynamically unstable within 25 Myr.

Predicted transit timing variations and libration centers.

Abstract

HD 110067 is the brightest star known to have six transiting planets. Each adjacent pair of planets has a period ratio that is nearly equal to a ratio of small integers, suggesting the planets are in a chain of mean-motion resonances, but the limited time span of the available data has prevented firm conclusions. Here, we show that the requirement of long-term dynamical stability implies that all six planets are very likely to form a resonant chain. Dynamical simulations of nonresonant systems with initial conditions compatible with the available data almost always suffer an instability within $25$ Myr ($\sim 0.3 \%$ of the system's age). Assuming the system is in resonance, we place upper limits on the planets' eccentricities and lower limits on the masses of the planets that have not yet been measured. We also predict the characteristics of transit timing variations and the values of the three-body libration centers.