The Radiational Mechanism And The Classification Of BL Lac Objects

We summarize the observational properties and theoretical models of BL Lac objects, introduce the studied history and actuality in detailed, sum up the basal theory of BL Lac objects roundly.There are four chapters in this thesis altogether. Chapter one briefly summarizes the defined character and classification of active galaxies nuclei (agns) presents the energy mechanism and unified schemes of agns. In chapter two we discussed the methods of detecting the BL Lac objects and the sample of BL Lac objects we used. After that, we give the up-to-date observational characters of BL Lac objects in different aspects, for example, optical variability, polarization, and so on. In Chapter three we review the theoretical models of BL Lac objects. Firstly, we briefly review the results of radiation mechanism, secondly, we discuss the different the theoretical models of BL Lac objects in detailed and stress the synchrotron self- Compton model in the frame of relativistic jet model. In this chapter we also briefly introduce some other models of BL Lac objects.The last chapter presents the result of our studies of how to use the peak frequency of synchrotron emission to classify the BL Lac objects and the action of the peak frequency in BL Lac objects. We sustain that the peak frequency can become a well classificatory criteria of BL Lac objects and conceive that there are some systemic difference between XBLs and RBLs, and the difference is not only the result of choice.