Further evidence for intra-night optical variability of radio-quiet quasars

TL;DR

This study presents observational evidence of intra-night optical variability in radio-quiet quasars, showing a low duty cycle and small amplitude variations, which supports the idea that INOV is less common in these objects compared to other active galactic nuclei.

Contribution

The paper provides new observational data on INOV in radio-quiet quasars, estimating the duty cycle and confirming the small amplitude of variability, thus contributing to understanding their variability behavior.

Findings

INOV detected in 2 clear and 2 probable cases among 11 RQQs.

Estimated INOV duty cycle of approximately 8%, rising to 19% including probable cases.

INOV amplitudes are small, around 1%, consistent with previous findings.

Abstract

Although well established for BL Lac objects and radio-loud quasars, the occurrence of intra-night optical variability (INOV) in radio-quiet quasars is still debated, primarily since only a handful of INOV events with good statistical significance, albeit small amplitude, have been reported so far. This has motivated us to continue intra-night optical monitoring of bona-fide radio-quiet quasars (RQQs). Here we present the results for a sample of 11 RQQs monitored by us on 19 nights. On 5 of these nights a given RQQ was monitored simultaneously from two well separated observatories. In all, two clear cases and two probable case of INOV were detected. From these data, we estimate an INOV duty cycle of $\sim$8% for RQQs which would increase to 19% if the `probable variable' cases are also included. Such comparatively small INOV duty cycles for RQQs, together with the small INOV amplitudes ($\sim$1%), are in accord with the previously deduced characteristics of this phenomenon.