SIMBAD references

In order to search for the evidence of quasi-periodic oscillation (QPO) in blazars, multicolor optical observations of the BL Lacertae object S5 0716+714 were performed from 2005 to 2012. 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 5.03×10⁶ M_☉ for a non-rotating Schwarzschild black hole and 3.2×10⁷ M_☉ for a maximally rotating Kerr black hole.