Study On Multi-band Variability Properties Of Blazar GTA 102

In this article,the classification and basic properties of AGNs are introduced in de-tail,and the most violent subclass of AGNs,namely the blazar,is analyzed and studied.The blazar is the main source of high-energy radiation in the extragalactic universe.The observation and analysis of its multi band light variation behavior is helpful for us to un-derstand the generation mechanism of high-energy radiation,reveal the origin of cosmic rays,and promote the study of extragalactic background radiation,galactic medium and galactic magnetic field.Blazars CTA 102 belongs to a high polarization flat spectrum radio quasar(FSRQs).In recent years,there have been two violent activities,in 2012 and 2016,respectively,and its peak flux reached F?2×10^-5ph cm^-2s^-1in the violent activities in 2016,and its ap-parent magnitude reached 11 mag,which may be the brightest blazars source of apparent magnitude observed so far.The research content of this article is focused on the multi band optical variation characteristics of high polarization source CTA 102,including fast optical variation,energy spectrum characteristics,correlation analysis of optical variation and correlation analysis between optical variation and polarization.We used Fermi-LAT observation data of gamma ray band of blaza CTA 102 for more than 10 years,combined with the observation data of optical band and optical polarization of Steward Observatory cooperating with Fermi observation mission,and added some ob-servation data of optical telescope YAO 1.02,studied the multi-band optical behavior and energy spectrum evolution characteristics of this source by asymmetric flare templates,discrete correlation function(DCF)and energy spectrum analysis.The main research results are in the following:the maximum magnitude variability during the whole obser-vation period are:?V=5.^m5??R=6.^m051,the fractional variability amplitude were V band respectively:F_var=8.827±0.443%,R band:F_var=9.340±0.489%.The analysis of asymmetric flare templates implies the minimal variability timescale are 0.359 days in V band,0.368 days in R band and 4.031 days in gamma band.The discrete correlation function(DCF)analysis shows that there is a significant correlation between multi-bands and no significant time lags are detected,which indicates that the radiation model of this source may be a single region leptonic radiation model.There is no correlation between the optical band and the polarization.We think that it may be caused by the thermal radi-ation of the accretion disk.There is no correlation between the gamma ray band and the polarization.It may be caused by the inverse Compton scattering of photons,which has nothing to do with the magnetic field.The energy spectrum analysis shows that there is a weak negative correlation between the magnitude and color index of the source,and be-tween the spectral index of gamma ray band and the flux,which indicates that the source may have a trend of becoming bright and blue(or dark and red).