Study Of The Multi-band Light Curve Of Blazars

In this paper,we focus on the multi-band light curve of a subclass of Active Galactic Nuclues（AGNs）;blazars have large,highly polarized multi-band light variations,and also have supermassive black holes at their centers and highly collimated central jets with respect to the observer.In the study of the multi-band light curves of blazars,some sources have been found to exhibit quasi-periodic oscillation（QPO）properties.However,the observed light curves are non-uniformly spaced due to weather、equipment failure,and some uncontrollable factors;and it is difficult to extract reliable QPO signals from these astronomical data using traditional methods.In this paper,we focus on how to extract reliable QPO signals from such light curves,and discuss some possible physical processes in conjunction with these results.In chapter 1,we introduce the basic observational features of AGNs,their classification,the properties of Spectral Energy Distribution（SED）,and the unified model and structure of AGNs.In chapter 2,the radiation mechanism of blazars and the derivation of the radiation model are introduced.In chapter 3,mainly introduces the different light-variation time scales and some corresponding physical processes.In chapter 4,mainly introduces the analysis methods of QPO;namely,the Lomb-Scargle Periodogram（LSP）method and the weighted wavelet Z-transform method（WWZ）as well as the methods of QPO signal significance estimation.In chapter 5,the results of multi-band light curve analysis of some blazars using LSP method and WWZ method are presented.（1）The analysis of the optical B,R,and I bands of BL Lac S5 0716+714 reveals a QPO of about 43 days with the corresponding confidence level greater than 99.7%;and the analysis of the spectrum index during the observation indicates that this QPO is likely to originate from the geometric variation in the jet.Therefore,we adopt a helical motion of a blob to explain it.（2）Analysis of the 15 GHz radio band of Blazars candidate J0210-1444 reveals a QPO of about 3.36 yr with a confidence level greater than 99.99%;we adopt a supermassive binary black hole to explain this QPO.（3）A QPO of about 1.1 years is found in the optical B,V,and R bands of FSRQ 0208-512;we adopt the hot spot on the accretion disk to explain this QPO,and further calculate the central black hole mass based on this assumption.（4）The analysis of FSRQ 3C 454.3 in the optical B,V,and R bands and the infrared J,K bands reveals a QPO of about 1.24 years;we adopt the hot spot on the accretion disk to interpret this QPO accordingly,and further calculate the central black hole mass based on this hypothesis.