The Multi-wavelength Radiation Mechanism Of BL Lac Objects

Blazars are radio loud active galactic nucleus with high luminance,high polarization,large and fast optical variation.As a subclass of blazar,the radiation of BL Lac objects covers all bands,from radio to gamma rays.Therefore,the study of BL Lac objects is of great significance for solving the physical model and energy radiation mechanism of the blazar.In this paper,based on the detailed description of the basic characteristics of the blazar,the physical process in the jet and the radiation model,the multi-wavelength radiation mechanism of BL Lac objects is studied.Assuming that shock wave propagates along the cylindrical jet,the electrons are continuously accelerated in the upstream of shock wave to gain energy,while in the downstream of the shock wave,a large amount of energy is released due to radiation cooling.According to the above assumptions,the particle distributions under four different conditions are established downstream of the shock wave,and the results are analyzed and discussed.Based on the SSC model,the SED of BL Lac object Mrk 421 was calculated by using the obtained particle distribution,and the calculated results were analyzed.The results show that:(1)Due to the cooling timescale of low-energy electrons is long,the low-energy part of the particle distribution does not contribute to SED;(2)Reasonable model parameters were selected,and the model calculation results were consistent with the multi-wavelength observation data of Mrk 421;(3)The contribution of the high-energy part of the particle distribution to SED and the change of the critical energy in the process of particle energy loss may lead to the change of SED in Mrk 421.In addition,we collect the multi-wavelength observation data of 40 high-peak-frequency TeV BL Lac objects with redshift,and calculate the SEDs of the samples based on the SSC model.The parameter distribution was obtained by using the model fitting results,and the jet physical parameters such as peak frequency,peak luminosity and jet power of synchrotron radiation and inverse Compton scattering were statistically analyzed.The results show that:(1)Compton dominant Ac are all less than 1,indicating that the radiation is dominated by SSC process;(2)There is a positive linear correlation between logvpeaksyn and logvpeaklc,and there is a positive linear correlation between log Lpeaksyn and log Lpeakic;(3)log Lpeaksyn and log Lpeakic have a positive linear correlation with the total jet power,the jet electron power and the jet proton power have a positive linear correlation with the total jet power.The above results prove that the SSC model can explain the multi-wavelength radiation of high-peak-frequency TeV BL Lac objects.