Top panel: GJ 628 measures of the and the Hα activity indices against BJD, where the presence of an activity cycle becomes evident: the red curve in the top row helps to guide the eyes. The black points represent our HARPS measurements, while the blue and red points depict measurements from Wright et al. (2004) and Isaacson & Fischer (2010), respectively, acquired with HIRES. A flare event occurs at BJD 2456481.6. Bottom panel: and Hα periodograms. The periodogram for HARPS+HIRES data (red curve) shows the activity cycle of 7000 days and a peak at about 400 days compatible with its yearly alias. Periodogram of the only HARPS (black curve) shows power excess at about 120 days while the one for Hα shows a clear peak at 64 days.