Simultaneous optical g, r, i monitoring and IDV periodic analysis for quasar 3C 454.3

With the 1.26 m National Astronomical Observatory-Guangzhou University Infrared/Optical Telescope (NAGIOT) at Xinglong Station of National Astronomical Observatories, Chinese Academy of Sciences, we obtained 419 groups of simultaneous observations at g, r and i bands, for the first time, targeting quasar 3C 454.3 during 15 nights from 2016 October 23 to 2016 December 15. Based on our observations, we investigate the optical variabilities, the relation between brightness and color index, and the periodicity variability. The presented analyses demonstrate that: 1. The maximum variations at the g, r and i bands are Δ m _g|max = 1.015 ± 0.042 mag, Δ m _r|max = 1.188 ± 0.050 mag and Δ m _i|max = 1.305 ± 0.057 mag respectively. 2. During our 15 night monitoring program, intra-day variability was detected on one night (Nov. 2). Also, the brightness increased by A = 15.86% over 50.8 min, then decreased by A = 22.42% over 40.1 min. After a small bright state, its brightness increased again by 18.1% over 55 min at the g band. Similar phenomena happened at r and i bands. The intra-day variabilities at the three bands on 2016 November 2 indicate a period of 105 min, which implies a black hole mass of M _BH = (0.3 ∼ 1.85) × 10⁹ M _⊙. 3. There is an anti-correlation between color index and magnitude, suggesting the source becomes redder when it brightens. (paper)