Search for Intra-day Optical Variability in γ-Ray-loud Blazars S5 0716+714 and 3C 273

Abstract

Abstract We present the photometric observations of blazars S5 0716+714 and 3C 273 with high temporal resolution (30–60 s) in the I or R bands. The observations were performed with a 1.02 m optical telescope from 2007 March 7 to 2012 May 16. The F-test, one-way analysis of variance (ANOVA) test, and z-transformed discrete correlation function (ZDCF) cross-correlation zero lag test are used to search for intra-day variability (IDV). Four and five reliable IDVs survive three tests for S5 0716+714 and 3C 273, respectively. IDVs are found for S5 0716+714 and 3C 273. A flare on 2008 May 8 has ΔI ≈ 0.06 ± 0.01 mag in a duration of 0.54 hr for S5 0716+714. A flare on 2011 May 10 shows ΔR ≈ 0.05 ± 0.01 mag in a duration of 0.40 hr for 3C 273. Sharp dips appear on 2011 May 9 for 3C 273 and show ΔR ≈ 0.05 ± 0.01 mag. Under the assumptions that the IDV is tightly connected to black hole mass, M •, and that the flare durations are representative of the minimum characteristic timescales, we can estimate upper bounds to M •. In the case of the Kerr black holes, M • ≲ 108.91 M ⊙ and M • ≲ 109.02 M ⊙ are given for S5 0716+714 and 3C 273, respectively. These mass measurements are consistent with those measurements reported in the literature. Also, we discuss the origins of optical variations found in this work.