Intranight optical variability of radio-quiet weak emission line quasars – II

Abstract

This is continuation of our search for the elusive radio-quiet blazars, by carrying out a sys- tematic programme to detect intranight optical variability (INOV) in a subset of ‘weak-line quasars’ which are designated as ‘high-confidence BL Lac candidates’ and are known to be radio-quiet. For 10 such radio-quiet weak-line quasars (RQWLQs), we present here the INOV observations taken in 16 sessions of durations ≳3.5 h each. Combining these data with our previously published INOV monitoring of RQWLQs in 13 sessions gives a set of INOV ob- servations of 15 RQWLQs monitored in 29 sessions, each lasting more than 3.5 h. The 29 differential light curves, thus obtained for the 15 RQWLQs, were subjected to a statistical analysis using the F-test, and the deduced INOV characteristics of the RQWLQs are com- pared with those published recently for several prominent AGN classes, also using the F-test. However, since the RQWLQs are generally 1–2 mag fainter, a rigorous comparison has to wait for somewhat more sensitive INOV observations than those presented here. Based on our existing INOV observations, it seems that RQWLQs in our sample show a significantly higher INOV duty cycle than radio-quiet quasars and radio lobe-dominated quasars. Two sessions when we detected rather strong (blazar-like) INOV for RQWLQs are pointed out, and both these RQWLQs are therefore candidates for radio-quiet BL Lacs.