MODELING THE TeV GAMMA-RAY SPECTRA OF TWO LOW-REDSHIFT ACTIVE GALACTIC NUCLEI: MARKARIAN 501 AND MARKARIAN 421

摘要

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 (γ_(max) ≥ 1.5 x 10~5). 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 γ_(max)mc~2 at which electrons are injected.