A Search for Blazar Activity in Broad-Absorption-Line Quasars

TL;DR

This study compares intra-night optical variability between BAL quasars with blazar-like properties and normal blazars, finding a significant difference likely due to jet-wind interactions affecting jet power and radio morphology.

Contribution

It provides the first rigorous INOV comparison between BAL_blazar candidates and normal blazars, revealing a stark contrast linked to jet-wind interactions.

Findings

Normal blazars show ~23% INOV duty cycle.

BAL_blazar candidates exhibit no INOV detection.

Jet-wind interactions may weaken jets and explain radio morphology differences.

Abstract

Our recently reported lack of Intra-Night Optical Variability (INOV) among Broad-Absorption-Line (BAL) quasars exhibiting some blazar-like radio properties, either questions polar ejection of BAL clouds, and/or hints at a physical state of the relativistic jet modified due to interaction with the thermal BAL wind on the innermost sub-parsec scale. As a robust check on this unexpected finding for the BAL_blazar candidates, we report here the INOV study of a new and much more rigorously defined comparison sample consisting of 9 normal (non-BAL) blazars, matched in both magnitude and redshift to the aforementioned sample of BAL_blazar candidates. The present campaign spanning 27 sessions yields an INOV duty cycle of ~23% for the comparison sample of normal blazars, employing the enhanced F-test. However, even this more sensitive test does not detect INOV for the sample of BAL_blazar candidates. This stark INOV contrast found here between the BAL_blazar candidates and normal blazars can probably be traced to a physical interaction of the relativistic jet with the thermal wind, within sub-parsec range from the nucleus. The consequent enfeebling of the jet would additionally explain the striking deficiency among BAL quasars of powerful FR II radio lobes on the much larger scale of 10-100 kpc.