The Hunt for Exomoons with Kepler (HEK): I. Description of a New Observational Project

TL;DR

This paper introduces the HEK project, a systematic effort to detect exomoons using Kepler data, employing Bayesian analysis to identify potential moon-hosting exoplanets and setting upper limits on moon occurrence.

Contribution

It presents the first comprehensive methodology for searching for exomoons in Kepler data, including target selection, light curve modeling, and Bayesian detection techniques.

Findings

Identification of promising exoplanet candidates for hosting moons

Development of a Bayesian framework for exomoon detection

Provision of upper limits on large moon frequency around exoplanets

Abstract

Two decades ago, empirical evidence concerning the existence and frequency of planets around stars, other than our own, was absent. Since this time, the detection of extrasolar planets from Jupiter-sized to most recently Earth-sized worlds has blossomed and we are finally able to shed light on the plurality of Earth-like, habitable planets in the cosmos. Extrasolar moons may also be frequent habitable worlds but their detection or even systematic pursuit remains lacking in the current literature. Here, we present a description of the first systematic search for extrasolar moons as part of a new observational project called "The Hunt for Exomoons with Kepler" (HEK). The HEK project distills the entire list of known transiting planet candidates found by Kepler (2326 at the time of writing) down to the most promising candidates for hosting a moon. Selected targets are fitted using a multimodal nested sampling algorithm coupled with a planet-with-moon light curve modelling routine. By comparing the Bayesian evidence of a planet-only model to that of a planet-with-moon, the detection process is handled in a Bayesian framework. In the case of null detections, upper limits derived from posteriors marginalised over the entire prior volume will be provided to inform the frequency of large moons around viable planetary hosts, eta-moon. After discussing our methodologies for target selection, modelling, fitting and vetting, we provide two example analyses.