Modelling the TeV γ - ray spectra of two low redshift AGNs

We discuss the results of modelling the TeV γ-ray spectra of two AGNs, Mkn 501 and Mkn 421 that have almost the same redshifts: z = 0.031 and z = 0.034, respectively. The effect of intergalactic γ-ray absorption is treated as an uncertainty in the measurement of the intrinsic spectrum. Although the objects differ, we obtain satisfactory fits for both of them in a synchrotron self-Compton scenario. Compared to previous models, our fits are characterised by higher values of the Doppler factor (δ ≥ 50) and an electron injection spectrum extending to higher energies (γ max ≥ 1.5 × 10 5). In the case of Mkn 421, the observed difference in spectral slope in X-rays and TeV γ-rays between the high and low states can be explained as a variation of a single parameter — the maximum energy γ max mc 2 at which electrons are injected.