Detectability of quasi-circular co-orbital planets. Application to the radial velocity technique

TL;DR

This paper introduces a criterion and a demodulation method to detect quasi-circular co-orbital exoplanets in radial velocity data, addressing the challenge of signal degeneracy and enabling inclination determination.

Contribution

It develops a new detectability criterion and a demodulation technique for identifying co-orbital planets in observational data, applicable across multiple detection methods.

Findings

The detection precision depends on libration amplitude and mass ratio.

The method can determine system inclination for tadpole orbits.

Applicable to radial velocity, transit, and astrometry data.

Abstract

Several celestial bodies in co-orbital configurations exist in the solar system. However, co-orbital exoplanets have not yet been discovered. This lack may result from a degeneracy between the signal induced by co-orbital planets and other orbital configurations. Here we determine a criterion for the detectability of quasi-circular co-orbital planets and develop a demodulation method to bring out their signature from the observational data. We show that the precision required to identify a pair of co-orbital planets depends only on the libration amplitude and on the planet's mass ratio. We apply our method to synthetic radial velocity data, and show that for tadpole orbits we are able to determine the inclination of the system to the line of sight. Our method is also valid for planets detected through the transit and astrometry techniques.