Systematic mischaracterization of exoplanetary system dynamical histories from a model degeneracy near mean-motion resonance

TL;DR

This paper investigates a degeneracy in radial velocity data that can cause misinterpretation of exoplanetary system architectures, revealing that 25% of analyzed systems may be incorrectly characterized as single planets.

Contribution

It introduces a Bayesian model comparison pipeline to quantify the rate of mischaracterization due to degeneracy near mean-motion resonance in exoplanet systems.

Findings

25% of systems show evidence for two-planet configurations

Degeneracy can lead to significant misunderstandings of system histories

New pipeline helps distinguish between single and multi-planet signals

Abstract

There is a degeneracy in the radial velocity exoplanet signal between a single planet on an eccentric orbit and a two-planet system with a period ratio of 2:1. This degeneracy could lead to misunderstandings of the dynamical histories of planetary systems as well as measurements of planetary abundances if the correct architecture is not established. We constrain the rate of mischaracterization by analyzing a sample of 60 non-transiting, radial velocity systems orbiting main sequence stars from the NASA Exoplanet Archive (NASA Archive) using a new Bayesian model comparison pipeline. We find that 15 systems (25% of our sample) show compelling evidence for the two-planet case with a confidence level of 95%.