Correlation between optical and $\gamma$-ray flux variations in BL Lacs

Abstract

We report here results on the analysis of correlated flux variations between the optical and GeV $\gamma$-ray bands in three bright BL Lac objects, namely AO\, 0235+164, OJ 287 and PKS 2155$-$304. This was based on the analysis of about 10 years of data from the {\it Fermi} Gamma-ray Space Telescope covering the period between 08 August 2008 to 08 August 2018 along with optical data covering the same period. For all the sources, during the flares analysed in this work, the optical and $\gamma$-ray flux variations are found to be closely correlated. From broad band spectral energy distribution modelling of different epochs in these sources using the one zone leptonic emission model, we found that the optical-UV emission is dominated by synchrotron emission from the jet. The $\gamma$-ray emission in the low synchrotron peaked sources AO\, 0235+164 and OJ 287 are found to be well fit with external Compton (EC) component, while, the $\gamma$-ray emission in the high synchrotron peaked source PKS 2155$-$304 is well fit with synchrotron self Compton component. Further we note that the $\gamma$-ray emission during the high flux state of AO 0235+164 (epochs A and B) requires seed photons from both the dusty torus and broad line region, while the $\gamma$-ray emission in OJ 287 and during epochs C and D of AO\,0235+164 can be modelled by EC scattering of infra-red photons from the torus.

17 pages, 26 figures, Accepted for publication in MNRAS (In the previous edition, a minor correction was made.)

References in corpus (22)

• Modeling the Emission Processes in Blazars
• The blazar sequence: a new perspective
• Simultaneous observations of PKS 2155-304 with H.E.S.S., Fermi, RXTE and ATOM: spectral energy distributions and variability in a low state
• The Outburst of the Blazar AO 0235+164 in 2006 December: Shock-in-Jet Interpretation
• Multi-wavelength observations of 3C 279 during the extremely bright gamma-ray flare in 2014 March-April
• General Physical Properties of CGRaBS Blazars
• Probing Acceleration and Turbulence at Relativistic Shocks in Blazar Jets
• Revisiting Quasi-Periodic modulation in $\gamma$-ray Blazar PKS 2155-304 with Fermi Pass 8 data
• Through The Ring Of Fire: $\gamma$-Ray Variability In Blazars By A Moving Plasmoid Passing A Local Source Of Seed Photons
• Temporal Correlations Between Optical and Gamma-ray Activity in Blazars
• Multi-wavelength observations of blazar AO 0235+164 in the 2008-2009 flaring state
• Multi-wavelength temporal and spectral variability of the blazar OJ 287 during and after the December 2015 flare: a major accretion disc contribution
• Optical quasi-periodic oscillation and color behavior of blazar PKS 2155-304
• Long term variability and correlation study of the blazar 3C 454.3 in radio, NIR and optical wavebands
• Temporal correlation between the optical and γ-ray flux variations in the blazar 3C 454.3
• Flux and polarization variability of OJ 287 during early 2016 outburst
• Correlation between optical and $\gamma$-ray flux variations in bright flat spectrum radio quasars
• A Two Zone Synchrotron Model for the Knots in the M87 Jet
• Optical Variability of TeV Blazars on long time-scales
• Long term optical and infrared variability characteristics of Fermi Blazars
• Intra-Night Optical Variability Monitoring of Fermi Blazars: First Results from 1.3 m J C Bhattacharya Telescope
• Unraveling The Complex Nature Of The Very High-Energy $\gamma$-Ray Blazar PKS 2155-304

Cited by in corpus (1)

• Study of correlation between optical flux and polarization variations in BL Lac objects