Confirming the 3:2 Resonance Chain of K2-138

TL;DR

This paper confirms the presence of a 3:2 resonance chain in the K2-138 planetary system through N-body simulations, constraining planetary properties and exploring formation scenarios.

Contribution

It provides the first detailed simulation-based confirmation of the 3:2 resonance chain in K2-138 and constrains planetary parameters using resonance analysis.

Findings

99.2% of simulations show a 3:2 resonance chain

11% of simulations show a five-planet resonance chain

Resonances help constrain orbital periods and planetary masses

Abstract

The study of orbital resonances allows for the constraint of planetary properties of compact systems. K2-138 is an early K-type star with six planets, five of which have been proposed to be in the longest chain of 3:2 mean motion resonances. To observe and potentially verify the resonant behavior of K2-138's planets, we run N-body simulations using previously measured parameters. Through our analysis, we find that 99.2% of our simulations result in a chain of 3:2 resonances, although only 11% of them show a five-planet resonance chain. We find we are able to use resonances to constrain the orbital periods and masses of the planets. We explore the possibility of this system forming in situ and through disk migration, and investigate the potential compositions of each planet using a planet structure code.