Total flux density variations in extragalactic radio sources. III. Dopplerboosting factors, lorentz factors, and viewing angles for active galactic nuclei

We have calculated Doppler boosting factors, D-var, for a sample of active galactic nuclei (AGNs) using total flux density variation monitoring data a t 22 and 37 GHz. We argue that this method is more accurate than the other commonly used methods based on the synchrotron self-Compton X-ray flux or e quipartition of energy. We compare our Doppler factors with other results a nd conclude that even if the average D-var for a class of sources is very s imilar to all others, the variability Doppler factors for individual object s are more accurate and reliable. An important application of precise Doppl er factors is presented, namely, calculating the Lorentz factors, Gamma, an d the viewing angles, theta, of relativistic outflows in AGNs. We find that high-polarization quasars have the greatest Doppler boosting, while low-po larization quasars and BL Lac objects are less boosted. The two groups of q uasars show different characteristics because of different combinations of the Lorentz factor and viewing angle, rather than either a different Gamma or theta alone.