The ever-surprising blazar OJ 287: multi-wavelength study and appearance of a new component in X-rays

Abstract

We present a multi-wavelength spectral and temporal investigation of OJ 287 emission during its strong optical-to-X-ray activity between July 2016 - July 2017. The daily $\gamma$-ray fluxes from \emph{Fermi}-LAT are consistent with no variability. The strong optical-to-X-ray variability is accompanied by a change in power-law spectral index of the X-ray spectrum from $<2$ to $>2$, with variations often associated with changes in optical polarization properties. Cross-correlations between optical-to-X-ray emission during four continuous segments show simultaneous optical-ultraviolet (UV) variations while the X-ray and UV/optical are simultaneous only during the middle two segments. In the first segment, the results suggest X-rays lag the optical/UV, while in the last segment X-rays lead by $\sim$ 5-6 days. The last segment also shows a systematic trend with variations appearing first at higher energies followed by lower energy ones. The LAT spectrum before the VHE activity is similar to preceding quiescent state spectrum while it hardens during VHE activity period and is consistent with the extrapolated VHE spectrum during the latter. Overall, the broadband spectral energy distributions (SEDs) during high activity periods are a combination of a typical OJ 287 SED and an HBL SED, and can be explained in a two-zone leptonic model, with the second zone located at parsec scales, beyond the broad line region, being responsible for the HBL-like spectrum. The change of polarization properties from systematic to chaotic and back to systematic, before, during and after the VHE activity, suggest dynamic roles for magnetic fields and turbulence.

arXiv comment13 pages, 4 figures, 2 tables, MNRAS accepted version

References in corpus (26)

• Measuring Reddening with SDSS Stellar Spectra and Recalibrating SFD
• The Large Area Telescope on the Fermi Gamma-ray Space Telescope Mission
• The Swift X-ray Telescope
• The Swift Ultra-Violet/Optical Telescope
• A Unifying View of the Spectral Energy Distributions of Blazars
• Pass 8: Toward the Full Realization of the Fermi-LAT Scientific Potential
• The First Swift Ultra-Violet/Optical Telescope GRB Afterglow Catalog
• Variability and stability in blazar jets on time scales of years: Optical polarization monitoring of OJ287 in 2005-2009
• The beaming pattern and spectrum of inverse Compton radiation in blazars
• Coordinated Fermi/Optical Monitoring of Blazars and the Great 2009 September Gamma-ray Flare of 3C 454.3
• Erratic Jet Wobbling in the BL Lacertae Object OJ287 Revealed by Sixteen Years of 7mm VLBA Observations
• Stochastic modeling of multiwavelength variability of the classical BL Lac object OJ 287 on timescales ranging from decades to hours
• Spatial growth of current-driven instability in relativistic rotating jets and the search for magnetic reconnection
• Measuring the spin of the primary black hole in OJ287
• Multi-band optical variability of three TeV Blazars on Diverse Timescales
• Improved AGN light curve analysis with the z-transformed discrete correlation function
• Short time-scale periodicity in OJ 287
• Multi-wavelength temporal and spectral variability of the blazar OJ 287 during and after the December 2015 flare: a major accretion disc contribution
• Multiband optical variability of the blazar OJ 287 during its outbursts in 2015 -- 2016
• High Energy Emission Processes in OJ 287 during 2009 Flare
• A peculiar multi-wavelength flare in the Blazar 3C 454.3
• Multi-band optical-NIR variability of blazars on diverse timescales
• Flux and polarization variability of OJ 287 during early 2016 outburst
• Gamma-ray Flare of PKS 1222+216 in 2010: Effect of Jet Dynamics at the Recollimation Zone
• Characterizing long-term optical, ultraviolet and X-ray variability in different activity states of OJ 287
• VERITAS detection of VHE emission from the optically bright quasar OJ 287

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• Long Term Multi-band Near Infra-Red Variability of the Blazar OJ 287 during 2007--2021
• Spectral States of OJ 287 blazar from Multi-wavelength Observations with $AstroSat$
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• Blazar OJ 287 After First VHE Activity: Tracking the Re-emergence of the HBL like Component in 2020
• Multi-wavelength temporal variability of the blazar PKS 1510-089
• A comprehensive study of 2019-2020 flare of OJ 287 using AstroSat, Swift, and NuSTAR
• X-ray Flux and Spectral Variability of the Blazar OJ 287 with Suzaku
• Exploration of the origin of 2020 X-ray outburst in OJ 287
• Temporal and Spectral Variability of OJ 287 before the April--June 2020 Outburst
• On the Spectral Changes of OJ 287: The Lowest X-ray state Spectrum -- extended at Optical-UV and Hard at X-rays
• The First VHE Activity of OJ 287 and the Extragalactic Background Light
• Simultaneous Optical to X-ray Spectra of OJ 287: Insights into X-ray spectral changes and particle spectra