Intra-night Optical Variability of BL Lacs, Radio-Quiet Quasars and   Radio-Loud Quasars
  We report optical monitoring observations of 20 high-luminosity AGN, 12 of which are radio-quiet quasars (RQQs). Intra-night optical variability (INOV) was detected for 13 of the 20 objects, including 5 RQQs. The variations are distinctly stronger and more frequent for blazars than for the other AGN classes. By combining these data with results obtained earlier in our program, we have formed an enlarged sample consisting of 9 BL Lacs, 19 RQQs and 11 lobe-dominated radio-loud quasars. The moderate level of rapid optical variability found for both RQQs and radio lobe-dominated quasars argues against a direct link between INOV and radio-loudness. We supplemented the present observations of 3 BL Lacs with additional data from the literature. In this extended sample of 12 well observed BL Lacs, stronger INOV is found for the EGRET detected BL Lacs. 
C. S. Stalin (1), A. C. Gupta (2), Gopal-Krishna (3), P. J. Wiita (4),   R.Sagar (5) ((1) IUCAA, Pune, (2) MRI, Allahabad, (...