2006ApJ...638..653K

H1426+428 is one of many blazars that are observed by γ-rays in the TeV region. Because TeV γ-rays from distant sources are subject to attenuation by the extragalactic background light (EBL) via electron-positron pair production, the intrinsic spectrum of the TeV γ-rays should be inferred by using the models of radiation processes and EBL spectrum. We set constraints on the physical condition of H1426+428 with the synchrotron self-Compton model applying several EBL models. We find that the emission region of H1426+428 is moving toward us with a bulk Lorentz factor of ∼20 and that its magnetic field strength is ∼0.1 G. These properties are similar to other TeV blazars such as Mrk 421 and Mrk 501. However, the ratio of the energy density of nonthermal electrons to that of the magnetic fields is about 190 and fairly larger than those of Mrk 421 and Mrk 501, which are about 5-20. We also find that the intensity of EBL in the mid- and near-infrared wavelengths should be low; i.e., the intensity at 10 µm is about 1 nW/m2/sr to account for the observed TeV γ-ray flux. Because the spectral data of H1426+428 in X-rays and γ-rays used in our analysis were not obtained simultaneously, further observations of TeV blazars are necessary to make the constraints on EBL more stringent.