Study On Multi-band Spectral Energy Distribution Of Blazar S4 0954+65

Blazars are a class of active galactic nuclei(AGN)with relativistic jets that are directed toward the Earth.Due to the Doppler beaming effect we observe full-wavelength emission mainly from the jets.The jets are composed of a large number of energetic particles,whose composition and production mechanism are still unknown,and their radiation mechanism is controversial.This thesis briefly introduces the background,basic properties and physical structure of active galactic nucleis and blazars and discusses the transport of energetic particles within the jets,focusing on the Fokker-Planck equations that include mechanisms describing first and second order Fermi acceleration,particle escape due to convection and spatial diffusion,and energy loss due to synchrotron radiation and inverse Compton scattering of the assumed soft photon field.In addition,this thesis introduces possible radiation mechanisms within the blazars,such as blackbody radiation,synchrotron radiation,Compton radiation,and gamma-gamma interaction,and focuses on the leptonic(synchrotron-Compton)radiation model.On this basis,the multi-band spectral energy distribution of the blazar S4 0954+65 was investigated and the following conclusions were obtained.(1)The multi-band spectral energy distribution properties of S4 0954+65 during the 2015 flare using the above particle transport models combined with the lepton synchronous-Compton model was explained.(2)S4 0954+65 was first detected TeV emission by the MAGIC telescope in the February 2015 flare,and the radiation in this band was reasonably fitted by introducing a soft photon field of 45000K.The thesis explores the origin of the soft photon field by suggesting the existence of weak clouds of broad emission lines of gas around the jet and the central black hole.