Forever alone? Testing single eccentric planetary systems for multiple companions

TL;DR

This study reevaluates apparent single-planet systems, finding that some may actually host multiple planets on nearly-circular orbits, which has implications for understanding their dynamical histories.

Contribution

The paper introduces a method to identify potential multiple-planet systems from existing single-planet data and confirms the stability of these configurations through dynamical tests.

Findings

Nine candidate systems identified for potential multiple planets

Some systems previously thought to have eccentric single planets are better explained by multiple near-circular planets

Dynamical stability confirmed for proposed multi-planet configurations

Abstract

Determining the orbital eccentricity of an extrasolar planet is critically important for understanding the system's dynamical environment and history. However, eccentricity is often poorly determined or entirely mischaracterized due to poor observational sampling, low signal-to-noise, and/or degeneracies with other planetary signals. Some systems previously thought to contain a single, moderate-eccentricity planet have been shown, after further monitoring, to host two planets on nearly-circular orbits. We investigate published apparent single-planet systems to see if the available data can be better fit by two lower-eccentricity planets. We identify nine promising candidate systems and perform detailed dynamical tests to confirm the stability of the potential new multiple-planet systems. Finally, we compare the expected orbits of the single- and double-planet scenarios to better inform future observations of these interesting systems.