EIC spectra calculated with different values of E ^b . Intrinsic EIC spectra (where the EBL attenuation is not taken into account) are shown at T = 10 ^2.6 s (thin) and T = 10 ^3.6 s (thick). The source redshift is set to z = 0.3. For the solid curves, the used parameter set is the same as that in the caption of Figure 3. The dotted curves are for E′ ^b = 10 ^2.5 eV and the dashed curves are for , while the other parameters are the same.