Modelling the Light Curves of Transiting Exomoons: a Zero-order Photodynamic Agent Added to the Transit and Light Curve Modeller

TL;DR

This paper enhances the Transit and Light Curve Modeller (TLCM) to include a photodynamic model for exomoons, enabling joint analysis of multiple transits and improving the detection capabilities of exomoon signals.

Contribution

The authors integrated a moon modeling feature into TLCM, allowing for the analysis of coplanar planet-moon systems with mutual eclipses, advancing exomoon detection methods.

Findings

No firm evidence of an exomoon in Kepler-1625b system.

Mutually eclipsing models can mimic exomoon signals.

Joint transit analysis improves detection reliability.

Abstract

Despite the ever-growing number of exoplanets discovered and the extensive analyses carried out to find their potential satellites, only two exomoon candidates, Kepler-1625b-i and Kepler-1708 b-i, have been discovered to date. A considerable amount of effort has been invested in the development of algorithms for modelling, searching, and detecting exomoons in exoplanetary light curves. In this work, we incorporate moon handling capabilities into the state-of-the-art and publicly available code, the Transit and Light Curve Modeller (TLCM). The code is designed for the analysis of transiting exoplanet systems with the inclusion of a wavelet-based noise handling algorithm. Here we present an updated version of TLCM that is capable of modelling a coplanar planet-moon system on an elliptical orbit around its host, accounting for mutual eclipses between the two bodies (and neglecting perturbative effects) -- a so-called photodynamic model. The key benefit of this framework is the ability for a joint analysis of multiple planet-moon transits. We demonstrate the necessity of this software on a case study of Kepler-1625b. Similarly to prior works, we conclude that there is no firm evidence of an exomoon in that system, by showing that temporally correlated noise can mimic apparent lunar transits.