Study On Multi-band Variability Of Gamma-ray Blazars

As a main extragalactic gamma-ray source,radiation covers the entire electromagnetic band making them effective probes for exploring the high-redshift universe.Multiband variability makes the study of its multi-band variation characteristics and spectrum variation characteristics an important means to understand the radiation mechanism of blazars.High-redshift blazars have been lack of comprehensive research due to the difficulty of observation.In this paper,high-redshift blazars are selected as the research objects,which is important for studying the high-energy radiation mechanism of blazars,limiting the model of extragalactic background light,and exploring the high-redshift universe.Based on the Fermi-LAT 4FGL Catalog,all 11 high-redshift blazars with redshift greater than 2.5 were screened out in this paper.High energy gamma-ray data from 100MeV to 300GeV covered 13 years were reduced.Combined with the observation data in the X-ray band of Swift and the optical band of ZTF monitoring project,the results of these high-redshift blazars have been analyzed.The following main research results were obtained:(1)The spectra of the 11 high-redshift blazars cannot be fitted by the Power-Law model,and their gamma-ray energy spectra are generally soft,(2)Five different EBL models were used to fit the energy spectra of high-redshift blazars.Under the premise that the intrinsic spectrum is a power-law spectrum,EBL model is inconsistent for different high-redshift blazars;(3)Using the Bayesian block method to verify the flare of each source,then fitting their light curve,we obtained the minimum variability timescale of the high-redshift blazars.The upper limits of their gamma radiation regions and their locations were estimated.These findings are extremely important for understanding the radiation mechanism of high-redshift blazars.However,due to the lack of high-quality simultaneous multiband observational data,it is impossible to study the origin of its high-energy flares,and there is no accurate restriction on the EBL models.