Abstract:
For a new sample of eight weak-line quasars (WLQs) we report a sensitive search in
20 intranight monitoring sessions, for blazar-like optical flux variations on hour-like and
longer time-scale (day/month/year-like). The sample consists exclusively of the WLQs that
are not radio-loud and either have been classified as ‘radio-weak probable BL Lac candidates’ and/or are known to have exhibited at least one episode of large, blazar-like optical
variability. Whereas only a hint of intranight variability is seen for two of these WLQs,
J104833.5+620305.0 (z = 0.219) and J133219.6+622715.9 (z = 3.15), statistically significant internight variability at a few per cent level is detected for three of the sources,
including the radio-intermediate WLQ J133219.6+622715.9 (z = 3.15) and the well-known
bona fide radio-quiet WLQs J121221.5+534128.0 (z = 3.10) and WLQ J153259.9−003944.1
(z = 4.62). In the rest frame, this variability is intraday and in the far-ultraviolet band. On
the time-scale of a decade, we find for three of the WLQs large brightness changes, amounting to 1.655 ± 0.009, 0.163 ± 0.010 and 0.144 ± 0.018 mag, for J104833.5+620305.0,
J123743.1+630144.9 and J232428.4+144324.4, respectively. Whereas the latter two are confirmed radio-quiet WLQs, the extragalactic nature of J104833.5+620305.0 remains to be well
established, thanks to the absence of any feature(s) in its available optical spectra. This study
forms a part of our ongoing campaign of intranight optical monitoring of radio-quiet WLQs,
in order to improve the understanding of this enigmatic class of active galactic nuclei and to
look among them for a possible tiny, elusive population of radio-quiet BL Lacs.
