Long-Period Giant Companions to Three Compact, Multiplanet Systems

TL;DR

This study characterizes three planetary systems with long-period giant companions and multiple short-period planets, providing insights into their formation and orbital dynamics.

Contribution

It presents new observations and analyses of three systems, including a newly discovered eccentric giant planet and improved mass constraints, advancing understanding of planet formation.

Findings

Kepler-65 hosts an eccentric giant planet exterior to a compact system.

Improved mass and radius estimates for Kepler-25 and Kepler-68.

Kepler-68 may have a second exterior giant planet candidate.

Abstract

Understanding the relationship between long-period giant planets and multiple smaller short-period planets is critical for formulating a complete picture of planet formation. This work characterizes three such systems. We present Kepler-65, a system with an eccentric (e=0.28+/-0.07) giant planet companion discovered via radial velocities (RVs) exterior to a compact, multiply-transiting system of sub-Neptune planets. We also use precision RVs to improve mass and radius constraints on two other systems with similar architectures, Kepler-25 and Kepler-68. In Kepler-68 we propose a second exterior giant planet candidate. Finally, we consider the implications of these systems for planet formation models, particularly that the moderate eccentricity in Kepler-65's exterior giant planet did not disrupt its inner system.