Using the 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 (probably another two) among them are classified as broad absorption line (BAL) quasars, with radio flux variations of a few 10 percent within 1.5-5 years. Such large amplitudes of the variations imply brightness temperatures much higher than the inverse Compton limits (1012 K) in all the BAL quasars, suggesting the presence of relativistic jets beaming toward the observer. The angle between the outflow and the jet is constrained to be less than ∼20∘. Such BAL quasars with polar outflows are beyond the simple unification models of BAL quasars and non-BAL quasars, which hypothesize that BAL quasars are normal quasars seen nearly edge-on.
@article{arxiv.astro-ph/0510243,
title = {Polar Outflows in Six Broad Absorption Line Quasars},
author = {Hongyan Zhou and Tinggui Wang and Huiyuan Wang and Junxian Wang and Weimin Yuan and Yu Lu},
journal= {arXiv preprint arXiv:astro-ph/0510243},
year = {2009}
}