1996A&A...310....1R

CCD multi-star photometry data was obtained on the BL Lac object AO 0235+164 to search for rapid variability. Light curves and photometric data are presented for this source in the B and V-bands. Intraday variability was recorded in both the B and V bands and AO 0235+164 was unusually bright at the time of the observations. Microvariability was also observed on four out of the six nights, and variations from 0.05 to 0.09 magnitudes occurred on time scales as short as 20 minutes. The rapid microvariability requires relativistic beaming for its explanation. The estimated size of the source is ∼10¹⁶cm assuming the variations are intrinsic to the relativistic jet in the BL Lac at a redshift z=0.94. The superluminal-microlensing scenario is also investigated because of the presence of an intervening giant elliptical or cD galaxy at z=0.524. An alternative explanation for the rapid optical microvariability is superluminal-microlensing of turbulent emission knots in the relativistic jet when they pass behind planets within the intervening galaxy.