Left: energy conversion into cosmic rays as a function of time for different η values (Eq. (1)), and compared with the best fit obtained from Naima. Vertical lines represent the crossing times of the inner radius of each shell. Scenarios for t_i = 1 d (green) and t_i = t_br (black) are displayed, both assuming E_cutoff = 1 PeV. Right: γ-ray flux expected from the interaction of each shell (η = 0.05) compared with the Fermi-LAT flux (100 MeV–100 GeV). The arrow represents the Bayesian block interval of the emission peak, while the TS is shown as shaded green bars. Both panels display the relevant time interval for the CSM shell model.