An analytical model for tidal evolution in co-orbital systems $\,$I. Application to exoplanets

TL;DR

This paper introduces an analytical Hamiltonian-based model to study tidal evolution in close-in co-orbital exoplanet systems, revealing stability conditions and potential for undetected companions.

Contribution

It extends the Hamiltonian formalism to include tidal dissipation effects in co-orbital systems, providing new criteria for their stability and detectability.

Findings

Co-orbital systems tend to favor Lagrange or anti-Lagrange configurations under tidal effects.

Both configurations are generally unstable over long timescales.

A practical criterion is proposed to identify potential undetected co-orbital exoplanets.

Abstract

Close-in co-orbital planets (in a 1:1 mean motion resonance) can experience strong tidal interactions with the central star. Here, we develop an analytical model adapted to the study of the tidal evolution of those systems. We use a Hamiltonian version of the constant time-lag tidal model, which extends the Hamiltonian formalism developed for the point-mass case. We show that co-orbital systems undergoing tidal dissipation either favour the Lagrange or the anti-Lagrange configurations, depending on the system parameters. However, for all range of parameters and initial conditions, both configurations become unstable, although the timescale for the destruction of the system can be larger than the lifetime of the star. We provide an easy-to-use criterion to determine if an already known close-in exoplanet may have an undetected co-orbital companion.