Revealing the Nature and Location of High Energy Emission in the
  Candidate Binary SMBH System OJ 287
  The latest flare of the regular $\sim$ 12 years quasi-periodic optical
outbursts in the binary SMBH candidate system OJ 287 occurred in December 2015.
Following this, the source has exhibited enhanced multi-wavelength (MW)
variability in spectral, temporal and polarization domains with new features
never seen before. Our MW investigation show that the overall MW variability
can be divided into two-phase, (i) November 2015 -- May 2016 with variability
from near-infrared (NIR) to Fermi-LAT $\rm \gamma$-ray energies (0.1 -- 300
GeV), and (ii) September 2016 -- July 2017 with intense NIR to X-ray
variability but without any activity in the Fermi-LAT band, and the very first
detection at very high energies (VHEs, E $>$ 100 GeV) by VERITAS. The broadband
SEDs during the first phase show a thermal bump in the NIR-optical region and a
hardening in the $\rm \gamma$-ray spectra with a shift in its peak. The thermal
bump like feature is consistent with the description of the standard
accretion-disk associated with the primary SMBH of mass $\sim 1.8\times10^{10}
M_\odot$ while the $\rm \gamma$-ray emission can be naturally reproduced by
inverse Compton scattering of photons from the broad line region which has been
seen during the close encounter duration of the binary SMBHs, thereby
suggesting a sub-parsec scale origin. The SEDs during the second phase (VHE
detection) is a mixture of typical OJ 287 SED with hardened $\rm \gamma$-ray
spectra and an HBL SED and can be explained in a two-zone model, one located at
sub-parsec scales and other at parsec scales. During both the phases, the MW
variability is simultaneous and almost always accompanied by changes in the
polarization properties, exhibiting random and systematic variations,
suggesting a strong role of magnetic field and turbulence.
