LONG-TERM MULTI-BAND PHOTOMETRIC MONITORING of BLAZAR S5 0716+714

Abstract

We present long-term optical multi-band photometric monitoring of blazar S5 0716+714, from 2004 January 11 to 2012 November 4, with high temporal resolution of approximately 15 minutes in the BVRI bands. The source was in an active state during the whole monitoring campaign, showing intraday variability in 11 of 72 days. The average magnitudes in each band were B = 14.398, V = 13.821, R = 13.255, and I = 12.885. The overall variability amplitudes were δB =1m834, δV =2m167, δR =2m148, and δI =1m912. The structure function showed that typical timescales for intraday variability were between approximately 2 and 7.5 hr. The intraday variability amplitudes were from a few percent to approximately 30%. We found typical variation rates of approximately 0.05 mag hr-1 in both the rising and falling phases, with a minimal variability timescale of 130 minutes. A 10 day period short-term variability was observed simultaneously in the BVRI bands. The discrete correlation function suggests that there is significant correlated variability between the B- and I-band light curves. However, no significant time lags were detected. The spectral behaviors in the different variability episodes were studied, and our observations show bluer-when-brighter behavior on long, short, and intraday timescales for the blazar S5 0716+714. The variability and relevant spectral trends can be explained by the shock-in-jet scenario.