Physical quantities describing the emitting region shown as a function of the bulk Lorentz factor Γ: the magnetic field strength in the comoving frame B′ (top panel), the number of emitting electrons N_e (second panel), the minimum Lorentz factor γ_m of the electron (third panel), and the distance R_γ of the emitting region from the central engine (bottom panel). At small Γ, solutions are limited by the requirement Y <  10. The pulse decay timescale t_γ is fixed to 1 s.