There exist a big dispute of the high energy emission of AGNs. Many models have been given to explain the radiation. Very high energy γ−ray flares of TeV blazars are generally accompanied with simultaneous active X-ray flares. However the observation of an “orphan” TeV flare of 1ES 1959+650 in 2002(without a simultaneous X−ray flare) is a challenge to standard leptonic synchrotron self-Compton (SSC) model. In addition the recent observation showing the loose correlation between X−ray and TeV γ−ray means that these two energy band photons may not emitted in the same regime, which also conflicts with SSC model. Here we give another model. We assume that high energy emission is produced by the accelerated protons in an inner blob near the black hole with a large magnetic field, while the low energy radiation comes from the electrons in the expanded blob. Under this situation the “orphan” TeV flares and the loose correlation between different energy band can be explained easily. Because the high and low energy photons are not produced in the same region, the requirement of large Doppler factor from pair production is relaxed. We present the estimations of the beaming Doppler factor in TeV Blazars based on the synchrotron self-Compton (SSC) uniform models from the observed low and high energy spectra. Using the high energy spectra corrected from the absorption of the intergalactic background light (IBL), we estimate the Doppler factors and the optical depths of gamma-ray absorption for eight TeV Blazars with multiwavelength data. We found that some sources have the modest values of Doppler factor and large optical depths. It implies that pair production is not avoidable. The high values of the Doppler factor appear in two objects of H 1426+428 and PKS 2155-304. It means that the uniform jet model faces difficult in explaining gamma-ray emission. The external Compton (EC) model is used to study the high energy emission of some blazars, in which the external photon field is considered to dominate inverse Compton radiation. We explore the properties of external photon field through analyzing the FERMI LAT bright AGN sample within three months detection. In the sample, assuming the high energy radiation of low synchrotron peaked blazars from the EC process, we find that the external photon parameter Uext/νext may not be a constant. Calculating synchrotron and inverse Compton (IC) luminosity from the quasi-simultaneous broadband spectrum energy distributions (SEDs), we find that they have an approximately linear relation. This indicates that the ratio of external photon and magnetic energy density is a constant in the comoving frame, implying that the Lorentz factor of the emitting blob depends on external photon field and magnetic field. The result gives a strong constraint on the jet dynamic model.
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