Theoretical SEDs in the rest-frame, which are normalized at 2000 Å for models with EW(Hα) = 500 Å (solid lines) and 100 Å (dashed lines) and different star formation timescales (constant SF in red and τ = 10 Myr in blue). For the models with EW(Hα) = 500 Å, the ages are 52 Myr and 16 Myr respectively. For EW(Hα) = 100 Å, 2.1 Gyr and 35 Myr.