Methods for exomoon characterisation: combining transit photometry and the Rossiter-McLaughlin effect

TL;DR

This paper explores how combining transit photometry and the Rossiter-McLaughlin effect can improve the detection and characterization of exomoons, especially their radius, orbital period, and density, through extensive simulations.

Contribution

It provides a detailed analysis of parameter reconstruction for exomoons using the RM effect and demonstrates the benefits of combining it with photometry for better constraints.

Findings

RM effect constrains moon radius effectively

Transit photometry helps determine moon mass

Combining methods allows density estimation

Abstract

It has been suggested that moons around transiting exoplanets may cause observable signal in transit photometry or in the Rossiter-McLaughlin (RM) effect. In this paper a detailed analysis of parameter reconstruction from the RM effect is presented for various planet-moon configurations, described with 20 parameters. We also demonstrate the benefits of combining photometry with the RM effect. We simulated 2.7x10^9 configurations of a generic transiting system to map the confidence region of the parameters of the moon, find the correlated parameters and determine the validity of reconstructions. The main conclusion is that the strictest constraints from the RM effect are expected for the radius of the moon. In some cases there is also meaningful information on its orbital period. When the transit time of the moon is exactly known, for example, from transit photometry, the angle parameters of the moon's orbit will also be constrained from the RM effect. From transit light curves the mass can be determined, and combining this result with the radius from the RM effect, the experimental determination of the density of the moon is also possible.