Afterglow from the forward shock. The assumed redshift and burst energy are z = 1 and ℰ_K = 4 × 10⁵² erg and the average Lorentz factor of the ejecta is . The theoretical light curves in the 0.3–10 keV energy range are presented (from top to bottom) for A_∗ = 1 to 10^-2 (dotted lines) and for n = 1 to 10^-6 cm^-3 (full lines). They are compared to the GRB 050421 data from the Burst Analyser (Evans et al. 2010).