2006ApJ...639..716Z

Using radio observations by FIRST and NVSS, we build a sample of 151 radio-variable quasars selected from the Sloan Digital Sky Survey Data Release 3 (SDSS DR3). Six (and probably another two) of these objects are classified as broad absorption line (BAL) quasars and show radio flux variations of a few tens of percent within 1.5-5 yr. Such large amplitudes of variations imply brightness temperatures much higher than the inverse Compton limits (10¹² K) in all these BAL quasars, suggesting the presence of relativistic jets beaming toward the observer. The angles between the outflow and the jet are constrained to be less than ∼20°. Such BAL quasars with polar outflows are beyond the simple unification models of BAL and non-BAL quasars, which hypothesize BAL quasars as otherwise normal quasars seen nearly edge-on.