(a) Transit geometry of the three-body system consisting of a star (large yellow circle), a planet (black circle), and a moon (orange and blue circles). The transit path across the star equals . (b) Illustration of an exomoon’s orbital sampling effect (OSE; Heller 2014; Heller et al. 2016a) in the light curve. The circumstellar orbital velocity of the barycenter (v_B) multiplied by the planet-moon orbital separation (r) defines the duration of the OSE feature before and after the planetary transit.