Abstract
There is now considerable evidence that bulk relativistic motion is common in the nuclei of radio-loud active galactic nuclei. Progress in relativistic beaming unified models during the last ten years is reviewed. It is suggested that classical BL Lacs and OW/HPQs should be treated separately because they appear to come from differently evolving populations and because the two classes of object have divergent properties. Strong cases can be made for the unification through beaming of lobe- and core-dominated quasars, and for unification of low luminosity (FR type 1) radio galaxies and classical BL Lacs. New emission line data support the view that the optical and X-ray continuum in all flat spectrum quasars, not just those known to be HPQ/OWs, is enhanced compared to that in steep spectrum quasars. The question of whether or not high luminosity (FRII) radio galaxies can be incorporated into the quasar scheme is discussed. If they can, the perceived strength of the narrow line [OIII]5007A emission must vary systematically with orientation.
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Browne, I.W.A. (1989). BL Lac objects, OW/HPQs and unified models. In: Maraschi, L., Maccacaro, T., Ulrich, M.H. (eds) BL Lac Objects. Lecture Notes in Physics, vol 334. Springer, Berlin, Heidelberg. https://doi.org/10.1007/BFb0031188
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DOI: https://doi.org/10.1007/BFb0031188
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