Modeling the TeV Gamma‐Ray Spectra of Two Low‐Redshift Active Galactic Nuclei: Markarian 501 and Markarian 421

Abstract

We discuss the results of modeling the TeV γ-ray spectra of two active galactic nuclei, Mrk 501 and Mrk 421, that have almost the same redshifts: z = 0.031 and 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 characterized by higher values of the Doppler factor (δ ≥ 50) and an electron injection spectrum extending to higher energies (γmax ≥ 1.5 × 105). In the case of Mrk 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 γmaxmc2 at which electrons are injected.