An Exomoon Survey of 70 Cool Giant Exoplanets and the New Candidate Kepler-1708 b-i

TL;DR

This study conducted a survey of 70 cool giant exoplanets from Kepler data, identifying a promising exomoon candidate, Kepler-1708 b-i, with statistical validation suggesting a potential new exomoon discovery.

Contribution

The paper presents the first systematic survey of cool giant exoplanets for exomoons, identifying a new candidate with robust statistical evidence.

Findings

Kepler-1708 b-i is a strong exomoon candidate with 4.8-sigma significance.

The candidate exomoon is approximately 2.6 Earth radii in size.

The exomoon candidate orbits at about 12 planetary radii from its host.

Abstract

Exomoons represent a crucial missing puzzle piece in our efforts to understand extrasolar planetary systems. To address this deficiency, we here describe an exomoon survey of 70 cool, giant transiting exoplanet candidates found by Kepler. We identify only one which exhibits a moon-like signal that passes a battery of vetting tests: Kepler-1708 b. We show that Kepler-1708 b is a statistically validated Jupiter-sized planet orbiting a Sun-like quiescent star at ~1.6AU. The signal of the exomoon candidate, Kepler-1708 b-i, is a 4.8-sigma effect and is persistent across different instrumental detrending methods, with a 1% false-positive probability via injection-recovery. Kepler-1708 b-i is ~2.6 Earth radii and is located in an approximately coplanar orbit at ~12 planetary radii from its ~1.6AU Jupiter-sized host. Future observations will be necessary to validate or reject the candidate.