Observation And Theoretical Study On Long-period Variability Of Blazars

Active galactic nucleus(AGNs)have become the forefront of contemporary astrophysics research because of its particularity.Blazars are the most special subclass of active galactic nuclei,the main difference is the lack or weakness of emission lines in BL Lac,BL Lac and FSRQs are known as Blazars because of their similar properties.Variability is an important part of studying the physical properties of various backgrounds and is one of the necessary ways to study the internal structure of AGN.It can provide an important breakthrough for astrophysics researchers.The paper firstly introduces the basic structure,characteristics,model of AGN and the radiation mechanism of the blazars.The second chapter discusses the observation characteristics,definitions,and CCD variability observations of the optical bands of the blazars,and provides a clear introduction to the CCD variability data processing of the lasing variants by the IRAF software.In the third chapter,we mainly describe the variability characteristics of blazars,the classification of variability time scales,the physical model of variability and the limitation of variability physical parameters of AGNs.The fourth chapter mainly describes the foundation of the optical variable period model through mathematical methods and then discusses four methods of long-period analysis.Four analytical methods are tested with a simulated periodic signaly=sin?.The results show that:(1)When the number of data points of blazars variability is relatively small to a certain value,the results of Jurkevich method,the time compensated discrete Fourier transform method(DCDFT),the discrete correlation analysis(DCF)and power spectral density analysis(PSD)are different.After obtaining the shortest continuous data points,the Jurkevich method may be the most accurate and reliable among the four methods,and the calculation method is simple and practical;(2)The optimal parameter of Jurkevich analysis method was obtained,and the results were the best when m=9;(3)The Jurkevich method at m=9 is used to analyze the variability of quasars 3C 279 and 3C 454.3.It is concluded that the possible variability of 3C 279 is(2.81±0.54)yr and 3C 454.3 is 457 days.In the fifth chapter,on the basis of collecting a large amount of data,the B-band and V-band variability of PKS 0735+178 are analyzed by the time compensated discrete Fourier transform,Jurkevich method,and discrete correlation analysis method.It is found that their periodic variability is(4.33 ±0.41)yr,and the lower limit of the mass of the central black hole is 0.22 × 10~6M(?).