Optical Intra-day Variability in Blazars

We selected a sample of a dozen blazars which are the prime candidates for simultaneous multi-wavelength observing campaigns in their outburst phase. We searched for optical outbursts, intra-day variability and short term variability in these blazars. We carried out optical photometric monitoring of nine of these blazars in 13 observing nights during our observing run October 27, 2006 − March 20, 2007 by using the 1.02 meter optical telescope equipped with CCD detector and BVRI Johnson broad band filters at Yunnan astronomical observatory, Kunming, China. From our observations, our data favor the hypothesis that three blazars: AO 0235+164, S5 0716+714 and 3C 279 were in the outburst state; one blazar: 3C 454.3 was in the post outburst state; three blazars: S2 0109+224, PKS 0735+178 and OJ 287 were in the pre/post outburst state; one blazar: ON 231 was in the low-state; and the state of one blazar: 1ES 2344+514 was not known because there is not much optical data available for the blazar to compare with our observations. We observed densely sampled 1534 image frames of these nine blazars. Out of three nights of observations of AO 0235+164, intraday variability was detected in two nights. Out of five nights of observations of S5 0716+714, intra-day variability was detected in two nights. In one night of observations of PKS 0735+178, intra-day variability was detected. Out of six nights of observations of 3C 454.3, intra-day variability was detected in three nights. No intra-day variability was detected in S2 0109+224, OJ 287, ON 231, 3C 279 and 1ES 2344+514 in their 1, 4, 1, 2 and 1 nights of observations respectively. AO 0235+164, S5 0716+714, OJ 287, 3C 279 and 3C 454.3 were observed National Astronomical Observatories/Yunnan Observatory, Chinese Academy of Sciences, P.O. Box 110, Kunming, Yunnan 650011, China. Center for Astrophysics, Guangzhou University, Guangzhou 510006, China Landessternwarte, Königstuhl 12, D 69117, Heidelberg, Germany