Vlbi Observations Of Ao 0235 +164, And Multi-band

In the text, the fundamentals of the VLBI observation and the whole processof data reduction, together with BL Lacertae objects, their properties and UnifiedSchemes are synthesized, analysed and reviewed, adding to some comprehension andopinion of myself. Special discussion and probe are placed on the object AO 0235+164,as a member of BL Lacertae, whose radio structrue and some special physical proper-ties, including VLBI observation and data post processing, periodic variation of the jetpositional angle, superluminal montion and the mass of the central engine are studiedand discussed. Additionally we also introduce a so-called discrete correlation function(DCF) method, and use it for correlation analysis of the flux densities in several wave-bands of AO 0235+164. The whole text consists in 6 chapters, which are describedseparately in the following:In Chapter one, the discovery and definition of BL Lacertae objects, the defini-tion and composition of AGN are described. Special stresses are put on the physicalproperties in optical, radio, X-ray and γ-ray wavebands, including the variability andpolarization in each waveband. Next, we reviewed the connection between RBLs and XBLs and the energy radiative process of BL Lacertae. Synchrotron radiation fromradio to optical band and inverse Compton Scattering in γ ray wavebands are a wideaccepted point. The beam model and gravitationally lensed model are two models as-sociated with the radiative process. At present people tends to favor the previous one.The Unified Scheme of AGN (including BL Lacertae objects) can be used to explainmany physical properties reasonably, but has yet to be further observations and confir-mation. In Chapter two, I first introduce the development of the radio astronomy andthe VLBI technique. Next the principal of the VLBI imaging, various corrections ofthe amplitude and phase, imaging methods and map quality evaluation are describedin relatively detail.From the beginning of Chapter 3, we study and discuss the radio structure andsome special physical properties of the object AO 0235+164 in detail. By virtue ofthe investigation and some previous VLBI observational results, we find the object ofrotational jet structure, and the radio spectrum of the object is very flat while its radiostructure is very simple, in addition, many evidences indicate that is a superluminalsource, but the apparent speed has been obtained with indirect way or under certain< VlIl>a,ss[llT1l)tiol1s. For tl1ese reasons, we apl2lied fOr VLBl observations from EVN and soong()L l)aSsed. Wi1,ll t1lc obsel.vatio11al l.esult ol1 epocll l997.l, a llew lligll l.esolutioll (2 lrlilli--arcsec) VLBl llybrid map of tlle BL Lacertae object AO 0235+l64 llas beellproduced at a wavelength of 6 cm. The map shows that the object(s radio structurejs dolnil1ated by a strong, nearly unreso1ved core. Clearly apparent are also a weakllortlleast, and a faint southwest component. The positional angle of the jet componentare equal to 66.4(, which is larger than any previous observation. In order to confirmtlle jet rotational guess, we fit the mu1ti-epochs jet positional angles with least squaremetllod, the results show that the jet has rotational period ranging from 3.46 year to3.74 year. Additiol1al method is a1so used to confirm our guess. With the monitoringresults of flux densities at 5 GHz, 8 GHz and 14.5 GHz and the Jurkevich's methodof period searching, we find that, the object ha8 bi-periodic variations in the threewaveballds, i.e., a shorter periodic variation of ~ 1 .8 year and a longer periodic variationof ~:j.6. 'l,lle bi--periodic variati()lls is l,l'obitbly tl1c l.csult of joillt actioll of tlle jetoutbursts alld jet rotation in a lJil1ary black hole system. Tlle longer periodic variationis collsistel1t with tllc lJeriodic variatiolls of the jet l,o8itiollaI allgle, wllicIl ilIlplies t)llattllc jet llligllt lJc illdeed ulldergoillg rotatil]g. Wllel...