Theoretically computed Lorentz factor for the parameter values ﹩E_{\mathrm{dya}\,}=9.57\times 10^{52}﹩ ergs and ﹩B=4\times 10^{-3}﹩ given as a function of the radial coordinate in the laboratory frame. The corresponding values in the comoving time, laboratory time, and arrival time are given in Table 1. The different eras, indicated by roman numerals, are illustrated in the text, while the points 1, 2, 3, 4, and 5 mark the beginning and end of each of these eras. The point P marks the maximum of the afterglow flux (see Ruffini et al. 2001b). At point 4, the transparency condition is reached.