The scattering outcomes of Kepler circumbinary planets: planet mass ratio

TL;DR

This study investigates how planet mass ratios influence the scattering outcomes of circumbinary planets, demonstrating that such interactions can explain observed orbital configurations of Kepler-34b and Kepler-413b.

Contribution

It introduces a model analyzing the effects of planet mass ratio and initial positions on scattering outcomes, reproducing observed planetary configurations.

Findings

Planet mass ratio significantly affects eccentricity distribution.

Scattering models can reproduce Kepler-34b and Kepler-413b configurations.

Both disk-driven migration and late-stage scattering shape planetary systems.

Abstract

Recent studies reveal that the free eccentricities of Kepler-34b and Kepler-413b are much larger than their forced eccentricities, implying that the scattering events may take place in their formation. The observed orbital configuration of Kepler-34b cannot be well reproduced in disk-driven migration models, whereas a two-planet scattering scenario can play a significant role of shaping the planetary configuration. These studies indicate that circumbinary planets discovered by Kepler may have experienced scattering process. In this work, we extensively investigate the scattering outcomes of circumbinary planets focusing on the effects of planet mass ratio. We find that the planetary mass ratio and the the initial relative locations of planets act as two important parameters which affect the eccentricity distribution of the surviving planets. As an application of our model, we discuss the observed orbital configurations of Kepler-34b and Kepler-413b. We first adopt the results from the disk-driven models as the initial conditions, then simulate the scattering process occurred in the late evolution stage of circumbinary planets. We show that the present orbital configurations of Kepler-34b and Kepler-413b can be well reproduced when considering two unequal-mass planet ejection model. Our work further suggests that some of the currently discovered circumbinary single-planet systems may be the survivals of original multiple-planet systems. The disk-driven migration and the scattering events occurring in the late stage both play an irreplaceable role in sculpting the final systems.