Flux and polarization variability of OJ 287 during early 2016 outburst
  The gamma-ray blazar OJ 287 was in a high activity state during December 2015
- February 2016. Coinciding with this high brightness state, we observed this
source for photometry on 40 nights in R-band and for polarimetry on 9 epochs in
UBVRI bands. During the period of our observations, the source brightness
varied between $13.20 \pm 0.04$ to $14.98 \pm 0.04$ mag and the degree of
polarization (P ) fluctuated between $6.0 \pm 0.3$% and $28.3 \pm 0.8$% in
R-band. Focusing on intra-night optical variability (INOV), we find a duty
cycle of about 71% using $\chi^2$-statistics, similar to that known for
blazars. From INOV data, the shortest variability time scale is estimated to be
$142 \pm 38$ min yielding a lower limit of the observed Doppler factor
$\delta_0 = 1.17$, the magnetic field strength $B \le 3.8$ G and the size of
the emitting region Rs < $2.28 \times 10^{14}$ cm. On inter-night timescales, a
significant anti-correlation between R-band flux and P is found. The observed P
at U-band is generally larger than that observed at longer wavelength bands
suggesting a wavelength dependent polarization. Using V -band photometric and
polarimetric data from Steward Observatory obtained during our monitoring
period we find a varied correlation between P and V-band brightness. While an
anticorrelation is seen between P and V -band mag at sometimes, no correlation
is seen at other times, thereby, suggesting the presence of more than one
short-lived shock components in the jet of OJ 287.
