Correlation between optical flux and polarization variations in Flat Spectrum Radio Quasars on diverse timescales

Abstract

Study of the polarization behaviour in blazars is a powerful tool to discern the role of magnetic field in the variable emission process in their relativistic jets. We present here results of our systematic investigation on the correlation between optical flux and polarization variations for eight flat-spectrum radio quasars on various timescales using data from the Steward Observatory that covers a period of $\sim$10 years. On long time scales ($\sim$several months), from a total of 79 observing cycles, in 34 observing cycles, we found a significant positive correlation between optical flux and optical polarization degree (PD), negative correlation in 3 cycles and no correlation in 42 cycles. On short time scales ($\sim$few days), in 47 out of a total of 55 epochs, we found a positive correlation between optical flux and PD, while, on the remaining 8 epochs, an anti-correlation was detected between the two quantities. Moreover, we noticed a significant positive correlation between optical and $\gamma -$ray fluxes on 14 epochs and a negative correlation between the two on one epoch. While the observed optical flux changes well fit in the shock-in-jet model, the observed changes in PD are not explainable by changes in the power-law spectral index of the relativistic electrons in the jet. Instead, the observed varied correlations between optical flux and PD could be due to multi-zone emission regions or the enhanced flux coinciding with the emergence of a new emission knot with its magnetic field either aligned or misaligned with the large scale magnetic field.

27 pages, 5 figures, 7 tables, accepted for publication in MNRAS main journal

References in corpus (29)

• Probing the Inner Jet of the Quasar PKS 1510-089 with Multi-waveband Monitoring during Strong Gamma-ray Activity
• The Sloan Digital Sky Survey Quasar Catalog: twelfth data release
• MAGIC discovery of VHE Emission from the FSRQ PKS 1222+21
• A change in the optical polarization associated with a gamma-ray flare in the blazar 3C 279
• MOJAVE: XV. VLBA 15 GHz Total Intensity and Polarization Maps of 437 Parsec-Scale AGN Jets From 1996-2017
• The Spectral Energy Distributions of Fermi Blazars
• RoboPol: The optical polarization of gamma-ray--loud and gamma-ray--quiet blazars
• RoboPol: Connection between optical polarization plane rotations and gamma-ray flares in blazars
• Blazar sequence - an artefact of Doppler boosting
• The Outburst of the Blazar AO 0235+164 in 2006 December: Shock-in-Jet Interpretation
• Temporal Correlations Between Optical and Gamma-ray Activity in Blazars
• X-ray Intraday Variability of Five TeV Blazars with NuSTAR
• Systematic Study of Gamma-ray bright Blazars with Optical Polarization and Gamma-ray Variability
• Quasi-periodic behaviour in the optical and γ-ray light curves of blazars 3C 66A and B2 1633+38
• Multiwavelength behaviour of the blazar 3C279: decade-long study from $\gamma$-ray to radio
• Multifrequency Studies of the Peculiar Quasar 4C +21.35 During the 2010 Flaring Activity
• Multi-frequency monitoring of gamma-ray loud blazars: I. Light curves and spectral energy distributions
• Clues on High Energy Emission Mechanism from Blazar 3C 454.3 during 2015 August Flare
• Temporal correlation between the optical and γ-ray flux variations in the blazar 3C 454.3
• Investigating the multiwavelength behaviour of the flat spectrum radio quasar CTA 102 during 2013-2017
• Long term γ -ray variability of blazars
• 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
• Broadband variability and correlation study of 3C 279 during flare of 2017-2018
• Multi-wavelength Temporal Variability of the Blazar 3C 454.3 during 2014 Activity Phase
• Multiwavelength Analysis of the Variability of the Blazar 3C 273
• Multiband optical flux density and polarization microvariability study of optically bright blazars
• Optical Variability of the TeV Blazar 1ES 0806+524 on Diverse Timescales
• Interpreting the variation phenomena of B2 1633+382 via the two-component model

Cited by in corpus (7)

• Gaussian Process Modeling Blazar Multiwavelength Variability: Indirectly Resolving Jet Structure
• Study of correlation between optical flux and polarization variations in BL Lac objects
• Multiwavelength analysis and the C IV λ1549 Å emission line behavior from 2008 to 2020 of the FSRQ B2 1633+382
• Flux and spectral variability of Mrk 421 during its moderate activity state using NuSTAR: Possible accretion disc contribution?
• Polarization Studies in Different Blazar Types. Part I: Correlation between Optical Brightness and Polarization Degree
• Investigating the origin of optical flares from the TeV blazar S4 0954+65
• Peculiar Behavior of Optical Polarization in Blazar 1ES 1959+650: Role of Jet Magnetic Field and Geometry