An exomoon survey of 70 cool giant exoplanets and the new candidate Kepler-1708 b-i

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 exhibiting 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 1.6 au. 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 similar to 2.6 Earth radii and is located in an approximately coplanar orbit at similar to 12 planetary radii from its similar to 1.6 au Jupiter-sized host. Future observations will be necessary to validate or reject the candidate.

Automated summary

Exomoons are an important missing puzzle piece in our understanding of extrasolar planetary systems. We conducted a survey of 70 cool, giant transiting exoplanet candidates found by Kepler, and found only one showing a moon-like signal. The planet is a statistically validated Jupiter-sized planet orbiting a Sun-like star.