Optical polarization variability and its relation to <i>γ</i> -ray activity in blazars

Optical polarization can be an important probe of particle acceleration and high-energy emission processes in relativistic jets from supermassive black holes. We combined publicly available observations from three past blazar monitoring programs to produce densely sampled light curves for 15 blazars in order to explore the relation of γ -ray activity to the polarization variability as well as discover new rotations of the polarization angle. We find that the polarization degree does not correlate with the γ -ray flux for individual sources nor different subsamples of blazars, potentially indicating multiple emission mechanisms. In the combined dataset, we identified a total of 64 rotations in 12 sources, 39 of which are newly identified rotations. We confirm the trend found in previous works for the whole sample: lower polarization degrees during periods of polarization angle rotations. However, looking at the individual sources, we identified cases where the rotation and non-rotation polarization degree distributions are indistinguishable, providing further evidence for the multiple emission mechanism hypothesis.