Top: H-α activity index of the 55 Cnc A star (see Fig. 2 of Bourrier et al. 2018a, second panel) and MOST observations dates (gray). Middle: combined H-α data phase folded at the planet orbital period. Bottom: amplitudes of the modulation (see Table 4) measured on MOST observations (black, left y-axis) and mean values of the H-α stellar activity indicator (red, right y-axis) evaluated around dates close to the MOST observations. The error bars on the mean H-α values are taken as the minimum and maximum values of the index in the considered year. We note the H-α values have been slightly shifted in time for visibility. We observe the increase/decrease of the modulation in phase with the increase/decrease of the stellar activity indicator.