Optical Monitoring of the Seyfert Galaxy NGC 4151 and Possible   Periodicities in the Historical Light Curve
  We report B, V, and R band CCD photometry of the Seyfert galaxy NGC 4151 obtained with the 1.0-m telescope at Weihai Observatory of Shandong University and the 1.56-m telescope at Shanghai Astronomical Observatory from 2005 December to 2013 February. Combining all available data from literature, we have constructed a historical light curve from 1910 to 2013 to study the periodicity of the source using three different methods (the Jurkevich method, the Lomb-Scargle periodogram method and the Discrete Correlation Function method). We find possible periods of P_1=4\pm0.1, P_2=7.5\pm0.3 and P_3=15.9\pm0.3 yr. 
Di-Fu Guo, Shao-Ming Hu, Jun Tao, Hong-Xing Yin, Xu Chen and Hong-Jian   Pan
astro-ph.HE astro-ph.GA