Testing One-zone Synchrotron-self-Compton Models With Spectral Energy Distributions Of Mrk 421

Blazar is a special subclass of active galactic nuclei(AGN),which have the relativistic jets orienting to us.The multi-band emissions covering from raido band to TeV energies are dominated by the non-thermal emission from the jet,and manifest rapid variability and high polarization.Fitting the quasi-simultaneous spectral energy distribution(SED)with emission models,one can obtain the physical parameters of the jet like magnetic field,the radius of the emission region,Doppler factor,etc.This will help us to understand the nature of the jet.Mrk 421 is one of the closest and brightest extragalatic TeV sources.Its synchrotron peak frequency is greater than 1015 Hz.The observations showed that Mrk 421 had rapid variability,and the accretion rate was low,and rare mattter is around its jet.A general accepted explanation of the SED is the one zone synchrotron self-Compton(SSC)model.However,we recently notice that the one zone SSC model seems to be challenged by new observation data.It is thus worth being tested more carefully.So we adopt high quality simultaneous observation data of Mrk 421 in 12 consecutive days,which is given in Aleksic et al.(2015).Then we use the MCMC technology to search the high dimension parameter space and obtain the model parameter errors.Due to the uncertainty of the electron energy distributions(EEDs),we use 3 types EEDs for the SED fittings:a log-parabola(LP)EED,a power-law log-parabola(PLLP)EED,a broken power-law(BPL)EED.We find that the one zone SSC model with PLLP EED can describe successfully these 12 observed SEDs.However,the one-zone SSC model with the LP and BPL EEDs fail to provide acceptable fits to the highest energy X-ray data or GeV data in several states.We therefor conclude that:(1)the one-zone SSC model works well in explaining the SEDs of Mrk 421,and the PLLP EED is preferred over the LP and BPL EEDs for Mrk 421 during the flare in March 2010;(2)We derive magnetic field B'?0.01 G,Doppler factor?D?30-50,and the curvature parameter of EED r?1-10;(3)we construct the evolution pattern of the model parameters,and discuss its physics.