Intranight Optical Variability of Radio-Quiet Weak Emission Line
  Quasars-III
  This is continuation of our programme to search for the elusive radio-quiet
BL Lacs, by carrying out a systematic search for intranight optical variability
(INOV) in a subset of `weak-line quasars' which are already designated as
`high-confidence BL Lac candidate' and are also known to be radio-quiet. For 6
such radio-quiet weak-line quasars (RQWLQs), we present here new INOV
observations taken in 11 sessions of duration >3 hours each. Combining these
data with our previously published INOV monitoring of RQWLQs in 19 sessions
yields INOV observations for a set of 15 RQWLQs monitored in 30 sessions, each
lasting more than 3 hours. The 30 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 then compared with those
published recently for several prominent AGN classes, also applying the F-test.
From our existing INOV observations, there is a hint 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 have detected strong (blazar-like)
INOV for RQWLQs are pointed out, and these two RQWLQs are therefore the best
known candidates for radio-quiet BL Lacs, deserving to be pursued. For a proper
comparison with the INOV properties already established for (brighter) members
of several prominent classes of AGN, a factor of 2-3 improvement in the INOV
detection threshold for the RQWLQs is needed and it would be very interesting
to check if that would yield a significantly higher estimate for INOV duty
cycle than is found here.
