The RINGO2 and DIPOL Optical Polarisation Catalogue of Blazars
  We present ~2000 polarimetric and ~3000 photometric observations of 15
gamma-ray bright blazars over a period of 936 days (11/10/2008 - 26/10/2012)
using data from the Tuorla blazar monitoring program (KVA DIPOL) and Liverpool
Telescope (LT) RINGO2 polarimeters (supplemented with data from SkyCamZ (LT)
and Fermi-LAT gamma-ray data). In 11 out of 15 sources we identify a total of
19 electric vector position angle (EVPA) rotations and 95 flaring episodes. We
group the sources into subclasses based on their broadband spectral
characteristics and compare their observed optical and gamma-ray properties. We
find that (1) the optical magnitude and gamma-ray flux are positively
correlated, (2) EVPA rotations can occur in any blazar subclass, 4 sources show
rotations that go in one direction and immediately rotate back, (3) we see no
difference in the gamma-ray flaring rates in the sample; flares can occur
during and outside of rotations with no preference for this behaviour, (4) the
average degree of polarisation (DoP), optical magnitude and gamma-ray flux are
lower during an EVPA rotation compared with during non-rotation and the
distribution of the DoP during EVPA rotations is not drawn from the same parent
sample as the distribution outside rotations, (5) the number of observed
flaring events and optical polarisation rotations are correlated, however we
find no strong evidence for a temporal association between individual flares
and rotations and (6) the maximum observed DoP increases from ~10% to ~30% to
~40% for subclasses with synchrotron peaks at high, intermediate and low
frequencies respectively.
