Upper panel: light curve of H.E.S.S. observations. The mean flux above 0.2 TeV per observing period (between two full moons) is shown as a function of the time in MJD. Only statistical errors are shown. Upper limits at 99% confidence level are calculated when no signal is found and in this case the corresponding negative fluxes are shown in magenta. The solid line represents the fit of a constant to the H.E.S.S. data. Middle panel: light curves of Fermi/LAT observations for the E_th > 300   MeV and E_th > 1   GeV thresholds in a 6-month binning. The first two flux points of the E_th > 300   MeV light curve and the first three flux points of the E_th > 1   GeV light curve have a TS < 9. Bottom panel: light curve of atom observations with R and B filters, corrected for Galactic extinction assuming E_B − V = 0.104 (case A).