The Hunt for Exomoons with Kepler (HEK): II. Analysis of Seven Viable Satellite-Hosting Planet Candidates

TL;DR

This study analyzes seven Kepler planet candidates for exomoons, finding no evidence of moons but setting upper limits on satellite-to-planet mass ratios, and providing precise transit measurements.

Contribution

The paper introduces a method for selecting promising exomoon host candidates and constrains satellite-to-planet mass ratios using Kepler data.

Findings

No compelling evidence for exomoons around the seven candidates.

Upper mass ratio limits suggest possible sub-Earth mass moons.

No dynamical variations observed in transit timings or durations.

Abstract

From the list of 2321 transiting planet candidates announced by the Kepler Mission, we select seven targets with favorable properties for the capacity to dynamically maintain an exomoon and present a detectable signal. These seven candidates were identified through our automatic target selection (TSA) algorithm and target selection prioritization (TSP) filtering, whereby we excluded systems exhibiting significant time-correlated noise and focussed on those with a single transiting planet candidate of radius less than 6 Earth radii. We find no compelling evidence for an exomoon around any of the seven KOIs but constrain the satellite-to-planet mass ratios for each. For four of the seven KOIs, we estimate a 95% upper quantile of M_S/M_P<0.04, which given the radii of the candidates, likely probes down to sub-Earth masses. We also derive precise transit times and durations for each candidate and find no evidence for dynamical variations in any of the KOIs. With just a few systems analyzed thus far in the in-going HEK project, projections on eta-moon would be premature, but a high frequency of large moons around Super-Earths/Mini-Neptunes would appear to be incommensurable with our results so far.