PoS - Proceedings of Science
Volume 329 - International Conference on Black Holes as Cosmic Batteries: UHECRs and Multimessenger Astronomy (BHCB2018) - Main session
Revealing the Nature and Location of High Energy Emission in the Candidate Binary SMBH System OJ 287
P. Kushwaha*, E.M. de Gouveia Dal Pino, A.C. Gupta and P.J. Wiita
Full text: pdf
Pre-published on: May 13, 2019
Published on: May 21, 2019
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.
DOI: https://doi.org/10.22323/1.329.0022
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