Light curve of Episode 2 in GRB 090618, ranging from 50 to 150 s. The dashed region represents the portion which would have triggered the Swift-BAT if this GRB had been at the redshift z = 8.2. The observed duration of that interval is approximately Δt ≃ 6 s. The results obtained in Fig. 6, when scaled to z = 0.54, provide ΔT ≃ 3 s.