Ringo2 Optical Polarimetry of Blazars

Abstract

We present polarimetric and photometric observations from a sample of 15 γ-ray bright blazars with data from the Tuorla blazar monitoring program (KVA DIPOL) and Liverpool Telescope (LT) Ringo2 polarimeters (supplemented with γ-ray data from Fermi-LAT). We find that (1) The optical magnitude and γ-ray flux are positively correlated; (2) electric vector position angle rotations can occur in any blazar subclass; (3) there is no difference in the γ-ray flaring rates in the sample between subclasses; flares can occur during and outside of rotations with no preference for this behaviour; (4) the average degree of polarisation (P), optical magnitude and γ-ray flux are lower during a rotation compared with during non-rotation; (5) the number of observed flaring events and optical polarisation rotations are correlated and (6) the maximum observed P increases from ∼10% to ∼30% to ∼40% for subclasses with synchrotron peaks at high, intermediate and low frequencies respectively.

Keywords

• galaxies
• active
• blazars
• polarisation