Multi-wavelength temporal and spectral variability of the blazar OJ 287
  during and after the December 2015 flare: a major accretion disc contribution
  We present a multi-wavelength spectral and temporal analysis of the blazar OJ
287 during its recent activity between December 2015 -- May 2016, showing
strong variability in the near-infrared (NIR) to X-ray energies with detection
at $\gamma$-ray energies as well. Most of the optical flux variations exhibit
strong changes in polarization angle and degree. All the inter-band time lags
are consistent with simultaneous emissions. Interestingly, on days with
excellent data coverage in the NIR--UV bands, the spectral energy distributions
(SEDs) show signatures of bumps in the visible--UV bands, never seen before in
this source. The optical bump can be explained as accretion-disk emission
associated with the primary black hole of mass $\sim \rm 1.8 \times10^{10}
M_{\odot}$ while the little bump feature in the optical-UV appears consistent
with line emission. Further, the broadband SEDs extracted during the first
flare and during a quiescent period during this span show very different
$\gamma$-ray spectra compared to previously observed flare or quiescent
spectra. The probable thermal bump in the visible seems to have been clearly
present since May 2013, as found by examining all available NIR-optical
observations, and favors the binary super-massive black hole model. The
simultaneous multi-wavelength variability and relatively weak $\gamma$-ray
emission that shows a shift in the SED peak is consistent with $\gamma$-ray
emission originating from inverse Compton scattering of photons from the line
emission that apparently contributes to the little blue bump.
