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Paper: Self-Similarity and Observed Properties in Blazars
Volume: 159, BL Lac Phenomenon
Page: 359
Authors: Georganopoulos, Markos; Marscher, Alan P.
Abstract: We propose a unification scheme for BL Lac objects (BLs) based on the angle Theta that describes the orientation of the relativistic jet and on the kinetic luminosity Lambdakin of the jet. We assume that Lambdakin scales with the size of the jet {r} in a self-similar fashion (Lambdakin propto r^2), as supported by observational data. The jets are self-similar in geometry and have the same pressure and median magnetic field at the inlet, independent of size. The self-similarity is broken for the highest energy electrons, which radiate mainly at high frequencies, since for large sources they suffer more severe radiative energy losses over a given fraction of the jet length. The negative apparent evolution of X-ray selected BLs is explained as a result of positive evolution of the jet kinetic luminosity Lambdakin. We review observational arguments in favor of the existence of scaled-down accretion disks and broad emission-line regions in BLs. The proposed unification scheme can explain the lack of observed broad emission lines in X-ray selected BLs, as well as the existence of those lines preferentially in luminous radio-selected BLs. Finally, we review observational arguments that suggest the extension of this unification scheme to all blazars.
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