Optical microvariability properties of BALQSOs

TL;DR

This study investigates optical microvariability in 19 radio-quiet BALQSOs over 13 nights, finding about 11% show microvariability, similar to normal RQQSOs, using a new scaled F-test for detection.

Contribution

It introduces a scaled F-test statistic for detecting microvariability and applies it to a larger sample of radio-quiet BALQSOs, providing new insights into their variability properties.

Findings

Approximately 11% of sources show microvariability.

Microvariability fraction similar to normal RQQSOs.

Supports models where RQ BALQSOs are not distinct in variability.

Abstract

We present optical light curves of 19 radio quiet (RQ) broad absorption line (BAL) QSOs and study their rapid variability characteristics. Systematic CCD observations, aided by a careful data analysis procedure, have allowed us to clearly detect any such microvariability exceeding 0.01--0.02 mag. Our observations cover a total of 13 nights (~72 hours) with each quasar monitored for about 4 hours on a given night. Our sample size is a factor of three larger than the number of radio-quiet BALQSOs previously searched for microvariability. We introduce a scaled F-test statistic for evaluating the presence of optical microvariability and demonstrate why it is generally preferable to the statistics usually employed for this purpose. Considering only unambiguous detections of microvariability we find that ~11 per cent of radio-quiet BALQSOs (two out of 19 sources) show microvariability for an individual observation length of about 4 hr. This new duty cycle of 11 per cent is similar to the usual low microvariability fraction of normal RQQSOs with observation lengths similar to those of ours. This result provides support for models where radio-quiet BALQSO do not appear to be a special case of the RQQSOs in terms of their microvariability properties.