3σ upper limit on the moon radius as a function of the mid-transit time shift ∆T₀ with respect to the planet and the transit duration W. The dotted white lines indicate the transit duration and location of planet v² Lup d. The horizontal axis spans the whole diameter of the Hill sphere (seen in projection on the stellar disc), where ∆T₀ < 0 indicates that the moon lags the planet. The bottom lines of the map show short transits that could represent a moon transiting shortly before being hidden by the planet, or transiting close to the limb of the star. Such short transits allow for larger moons to exist while remaining undetectable in our single-epoch data set.