Validation of Exomoon Candidates Using Orbital Stability and Tidal Migration

Satellites of extrasolar planets, or exomoons, are on the frontier of detectability using current technologies and theoretical constraints should be considered in their search. We apply theoretical constraints of orbital stability and tidal migration to six candidate KOI systems that are proposed to host exomoons. We find that the orbital stability extent of exomoons for these systems is limited to only ~20 planetary radii because the host planet orbits so close the host star. Moreover, four out of six systems would either tidally disrupt their exomoons or lose them to outward tidal migration within the system lifetimes when considering plausible tidal parameters from the solar system. The remaining two systems (KOI 268.01 and KOI 1888.01) could support exomoons over the system lifetime but are limited to ~3% of the host planet’s mass and orbit within 25 planetary radii. Observational signatures through transit timing variations could validate these systems, but the combined constraints of tidal migration and orbital stability place these systems on the border of detectability. Tools to reproduce our analysis are available in the GitHub repository: Multiversario/satcand.