Emission in the co-moving frame: Effect of the electron Lorentz factor. Starting from the reference case shown in red (Γ_m = 1600, B′₀ = 2000 G, n_e, acc = 4.1 × 10⁷ cm⁻³, t_dyn = 80 s), we plot the evolution of the spectrum when varying the electron Lorentz factor, either assuming a constant (left) or a decaying (right) magnetic field. The adopted values are Γ_m = 51 (cyan), 160, 510, 1600, 5100, 1.6 × 10⁴, 5 × 10⁴, and 1.6 × 10⁵ (magenta). The spectra obtained when pair production and synchrotron self-absorption are not included are shown with thin lines. Dashed lines show the spectra that do not satisfy the conditions for transparency (τ_T < 0.1) or that are radiatively inefficient (f_rad < 50%).