We monitored the BL Lac object S5 0716+714 in four optical wavebands with four telescopes on 11 nights from 2012 to 2017. The object was active during most of those nights. It was brightest on 2012 November 7 with 11.720 mag in the I band and reached the faintest state on 2016 January 22 with 15.770 mag in the R band corresponding to ∼15.230 mag in the I band. Intraday variations in all bands were found on 6 d, while in partial bands on 3 d. Strong bluer-when-brighter chromatism was observed on 8 nights. Correlation analyses revealed interband time delays from 4 to 40 min in the intraday variability on 5 nights. Both hard and soft lags were observed in this object, indicating complicated emission process in the jet. The analysis on the interband time delays indicated that the radiative cooling may dominate the optical time lags in S5 0716+714 occasionally, but cannot be invoked as the sole explanation.

中文翻译：

---

BL Lacertae 天体 S5 0716+714 的日内多波段光学变异性

从 2012 年到 2017 年的 11 个晚上，我们用四个望远镜在四个光学波段监测了 BL Lac 天体 S5 0716+714。该天体在这些夜晚的大部分时间里都很活跃。它在 2012 年 11 月 7 日最亮，I 波段为 11.720 等，并在 2016 年 1 月 22 日达到最暗状态，R 波段为 15.770 等，对应于 I 波段~15.230 等。6 d发现所有波段的日内变化，而3 d发现部分波段。在 8 个晚上观察到强烈的更亮时更蓝的色差。相关性分析揭示了 5 晚的日内变化中的带间时间延迟从 4 到 40 分钟。在该物体中观察到硬滞后和软滞后，表明射流中的发射过程复杂。