Intraday optical variability of the BL Lacertae object S5 0716+714




The intraday optical variability of the BL Lacertae object S5 0716+714 is studied using historical light curves. The well-sampled intranight data set is selected. In total, 19 333 data points have been collected over 208 nights. The source exhibits strong variability in the optical band. At a confidence level of 99.9 per cent, for 162 of the 208 nights the source shows intranight variability. The source varies with an increasing rate of 0.043 mag h−1 and a decreasing rate of 0.036 mag h−1 during the observations, with no evident difference between rising and falling parts. The fast variability is found on JD 245 1909, with a decreasing rate of 0.015 mag min−1 over 6 min. The temporal characteristic is studied by using the structure function method. The result shows that the source varies with an 11.5-min time-scale. For this source, the emission size is estimated to be 1.39 × 1014 cm, the mass of the central black hole is estimated to be 107.87 M and the magnetic field strength is estimated to be 10.6 G.