Kepler observations of Kepler-139 over time ranges when transits of planet f would be expected. Each panel spans the 90% confidence range of transit times predicted by the five-planet model (Table 1). Transits of planets b and c are highlighted in blue and green. The expected transit signals for planet f, assuming R_p  =  4 R_⊕ and b  =  0.5, are shown in orange. Such signals would have been easily detectable but are not seen.