A search for the elusive radio-quiet BL Lacs

Parveen Kumar1*, Hum Chand1, Gopal-Krishna2 and Ravi Joshi3
1ARIES, Manora Peak, Nainital 263002, India
2CBS, University of Mumbai campus (Kalina), Mumbai 400098, India
3IUCAA, Postbag 4, Ganeshkhind, Pune 411 007, India

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Two years ago, we started a 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 emission line quasars which are already designated as high-confidence BL Lac candidate and are also known to be radio quiet. We monitored 15 such radio-quiet weak emission line quasars (RQWLQs) over 30 sessions in R-band with typical exposure of 5 − 8 minutes. Each object was observed more than 3.5 hrs, using the 1.3m telescope at Devasthal, India. These 30 differential light curves are subjected to a statistical analysis using F−test. In our study, we detected strong (blazar-like) INOV for two session in two RQWLQs and hence these are designated as the best known candidates for radio-quiet BL Lacs, deserving to be pursued further.

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Keywords : galaxies-active -BL Lacertae objects, emission line- quasars.