H.E.S.S. light curve (red) above 310 GeV derived from the stereo data in this work compared to the Fermi-LAT light curve (blue) above 100 MeV (scaled down with 10⁻²) with a bin size of ∼60 days. The dashed lines represent the periastron passages of 2014 and 2020 at phases 0 and 1, respectively. The error bars correspond to the 68% confidence interval and upper limits (at 95% confidence) were calculated for phase bins with a less than 2 σ detection significance.