Intranight optical variability of radio-quiet BL Lacertae objects

TL;DR

This study monitored eight radio-quiet BL Lac objects over multiple nights and found no significant intranight variability, suggesting their emission is not jet-dominated like in radio-loud BL Lacs.

Contribution

First systematic photometric monitoring of radio-quiet BL Lac objects to assess their intranight variability properties.

Findings

No significant microvariations detected in 11 sessions.

Microvariation rate similar to radio-quiet AGNs.

Lower than variability in radio-loud AGNs.

Abstract

Aims: Intranight variation (or microvariation) is a common phenomenon of radio-loud BL Lac objects. However, it is not clear whether the recently found radio-quiet BL Lac objects have the same properties. The occurrence rate of intranight variation is helpful in distinguishing the mechanism of the continuum of radio-quiet BL Lac objects. Methods: We conducted a photometric monitoring of 8 radio-quiet BL Lac objects by the Xinglong 2.16m and Lijiang 2.4m telescopes. The differential light curves are calculated between each target and two comparison stars. To quantify the variation, the significance of variation is examined by a scaled $F$-test. Results: No significant variation is found in the 11 sessions of light curves of 8 radio-quiet BL Lac objects (one galactic source is excluded). The lack of microvariation in radio-quiet BL Lac objects is consistent with the detection rate of microvariation in normal radio-quiet AGNs, but much lower than for radio-loud AGNs. This result indicates that the continua of the radio-quiet BL Lac objects are not dominated by jets that will induce frequent microvariations.