2005-2012 BVRI observations of blazar S5 0716+714

For I band observations on 2010 March 19 with low variability amplitude and low flux level, the same QPO~50 minutes at the 99% significance level is confirmed by the ZDCF method, Lomb-Scargle method, REDFIT, and fitting sinusoidal curves.

The observed QPO is likely to be explained by accretion disk variability. If the observed QPO indicates an innermost stable orbital period from the accretion disk, the QPO~50 minutes corresponds to a black hole mass of 5.03x10^6^ M_{sun}_ for a non-rotating Schwarzschild black hole and 3.2x10^7^ M_{sun}_ for a maximally rotating Kerr black hole.