Optical EVPA rotations in blazars: testing a stochastic variability model with RoboPol data

We identify rotations of the polarization angle in a sample of blazars observed for three seasons with the RoboPol instrument. A simplistic stochastic variability model is tested against this sample of rotation events. The model is capable of producing samples of rotations with parameters similar to the observed ones, but fails to reproduce the polarization fraction at the same time. Even though we can neither accept nor conclusively reject the model, we point out various aspects of the observations that are fully consistent with a random walk process.
Comment: 17 pages, 18 figures, 4 tables. Accepted 2017 August 17 for publication in MNRAS