Light-curve (top panel) and photospheric velocities (bottom panel) for our reference model (see text) shown in blue solid line, corresponding to a magnetar with E_rot = 10 foe and t_p = 1 d. A characteristic maximum luminosity L_max is derived as the mean of the three local maxima found in the LC (red dots). The intersection of the horizontal line defined as logL_max − 0.2 dex, with the LC provides the estimated temporal extent of that maximum, Δt. For comparison, we show the same SN model without a magnetar with dashed gray lines.