Study On The Multiband Variability And Radiation Mechanism Of The FSRQS

The trigh-energy(HE)gamma-ray emission mechanism of blazar has always been an open problem.The observational study of high-energy gamma-ray emission has become a probe to solve this problem.Flat spectrum radio quasars(FSRQs),a subclass of blazars,are the main extragalactic gamma-ray sources.The study on high radiation of FSRQs with multi-band observation will shed light on the origin of cosmic rays,the acceleration of high-energy particles,the extragalactic background radiation and the production mechanism of jet.We collected and processed the long-term multi-band observations of 4 typical FSRQs from radio to high-energy gamma-rays energy bands.Combining with the Bayesian blocks method and long-term average fluxes of gamma-ray,we improve a method to judge whether the flare is or not.Through the correlation analysis among different energy band,fitting and calculating the minimum variability time scale,comparing the variability amplitude of each energy band,and fitting the spectral energy distributions(SEDs)of each source in different states by using the leptonic model,we discuss the variability properties of the multi-band behavior of FSRQs,the location of gamma-ray flare,the size of the radiation region,and the power change along with the evolution of energy spectrum.The following main results are obtained.The most FSRQs have a dense high-energy radiation region structure of order～1015 cm.It is located within the boundary of the broad-line region(BLR),near the base of the jet.It is found that GB 1310+487 has the shortest time-scale of order of hour,but not the day-scale reported in literature.The emission of flare of FSRQs maybe caused by diffuse shock and may also be related to magnetic reconnection.The 4 FSRQs all have short-term variability.The injected electron spectral index of the 4 FSRQs is in the range of 1.5 to 2.6.When the source variable from quiet state to flare state,the magnetic field intensity decreases,indicating that Poynting energy is consumed in the flare process.The jet of FSRQs are dominated by particles or matter.For the 4 sources,the electron energy density is several or even tens of times larger than the magnetic field energy density while in the flare state.This imply that the increase of electron density in the radiation region is one of the reasons resulting to the high-energy flare.The jet radiative power of 4 sources shows a weak positive or no correlation with the black hole mass,suggesting that both black hole accretion and rotation may be responsible for the generation of jets of FSRQs.