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Session 56 - BL Lacs & Blazars.
Oral session, Thursday, January 08
Georgetown,
BL Lacertae (BL Lac) objects have been traditionally classified as radio selected BL Lacs (RBLs) or X-ray selected BL Lacs (XBLs) according to the discovery method. The recent discovery of a BL Lac population with observational properties intermediate between those of RBLs and XBLs, strongly suggest that this bimodal classification is misleading, and essentially reflects the two different discovery methods.
We propose a unification scheme for BL Lac objects based on the following scenario: the kinetic luminosity of the jet \Lambda_kin scales with the size of the jet r, following the relation \Lambda_kin\propto r^2. Additionally, the intensive physical variables that describe the relativistic jet in the BL Lac objects have a small intrinsic range of values. The combination of these two assumptions suggests a unification scheme, where the observed properties of a BL Lac depend mainly on the kinetic luminosity of the jet and the angle between the line of sight and the jet axis. We apply this scheme using the accelerating inner jet model, comparing the predictions of this unification with observational data from complete BL Lac samples. Finally, we briefly address the question of extending this unified scheme to include the family of flat spectrum radio quasars.
