Blazars Optical Variable Characteristics And Evolution

In this thesis, we review the basic properties and major characteristics about the active galactic nuclei (AGNs), specially, we focus on the observations, timescale and periodicity of the variability in blazars. We also summarize the theory model of blazers. Some studies for evolution of the AGNs and some of our research for blazars are present hereOur main works and results are as follow: (1) studying on short timescale variability of blazars. The observational results monitored by our CCD photometry for 31 blazars show that the short timescale (-hours) variability is a notable property for blazar observation. Usually the variability of the blazars which brightness fluctuated more than 0. 5 mag within one or several hours could be monitored in optical band (B, V, R, I). We even observed the violently rapid variation which magnitude decreased larger than 1 mag within 1 hour (e.g. PKS 1510-089). For this rapid variability phenomenon, there is not any suitable theoretical explanation, however this also reflect the structure of emission region and a supermassive black hole in its center. (2) Variabilities on a medium time-scale of one or several months were observed in some blazars. We find that 3C 66A has a variability period of 63 + 5 days, supporting the 65 days period obtained by Lainela et al. (1999). (3) studying on long timescale variability of blazars. The studies of blazars which have light curve with long time span show periodicity for long timescale variability. For PKS 1510-089, based on the fact of three rapid and large-amplitude variations with very deep minima observed during 1999-2001, we predicted that this phenomenon would occur repeatedly and would be observed. The dense monitoring in 2002 March confirm the prediction and it is the first successful repeat observation for this kind of phenomenon. A hypothesis that suggesting a binary black hole system at the centre of PKS 1510-089 is proposed to interpret the phenomenon. The parameters of the system are estimated as: the masses of the primary and secondary black holes are 108.0M⊙和106.2⊙, repectively; the distance between two black holes is 1015.81cm, and the lifetime of the system is 1060 yr. (4) studying onvariability timescale by structure function (SF) analysis and periodicity analysis by multi-means. The behavior exhibited by SF plot for short-timescale variability is of the following types: that is no plateau even at long time lag, one plateau or multi-plateau in SF of the sources. These possibly be relate to different physical processes in sources. For exactly determining the periodicity in long-term light curve, Jurkevich Vm2 method, structure function, power density spectrum and folded light curve analysis method are suggested simultaneously. (5) studying on evolution sequence of the blazars. The mass distribution, mass-intrinsic luminosity relation and accretion rate-intrinsic luminosity for a sample of 39 blazars with well-established rapid variability timescale and bolometric luminosity complied from the literature have been investigated. Analysis reveals a relationship of log(Lin/L⊙)=1.225log(M/M⊙) + 1.500 both for FSRQs and BL Lacs objects. The diagram of the intrinsic accretion rate-luminosity relations shows that the evolutionary track of the elliptical galaxy evolutionary sequence is from FSRQs to BL Lac objects and then to the radio galaxies. The results is consistent with the evolutionary sequence proposed in the dual jet theories by Punsly (1996). There are five chapters in this thesis altogether. Chapter one is an overview of basic properties and major characteristics about the active galactic nuclei (AGNs). Chapter two presents observation characteristic of blazars, such as timescale, spectral energy distributions and polarization. Chapter three introduces some theory model for studying blazars. Chapter four presents some researching work for observations, timescale characteristic and periodicity of blazers. Chapter five introduces some researching work for evolution of the blazer.