Multiwavelength behaviour of the blazar 3C279: decade-long study from $\gamma$-ray to radio

Abstract

We report the results of decade-long (2008-2018) $\gamma$-ray to 1 GHz radio monitoring of the blazar 3C 279, including GASP/WEBT, $Fermi$ and $Swift$ data, as well as polarimetric and spectroscopic data. The X-ray and $\gamma$-ray light curves correlate well, with no delay > 3 hours, implying general co-spatiality of the emission regions. The $\gamma$-ray-optical flux-flux relation changes with activity state, ranging from a linear to a more complex dependence. The behaviour of the Stokes parameters at optical and radio wavelengths, including 43 GHz VLBA images, supports either a predominantly helical magnetic field or motion of the radiating plasma along a spiral path. Apparent speeds of emission knots range from 10 to 37c, with the highest values requiring bulk Lorentz factors close to those needed to explain $\gamma$-ray variability on very short time scales. The Mg II emission line flux in the `blue' and `red' wings correlates with the optical synchrotron continuum flux density, possibly providing a variable source of seed photons for inverse Compton scattering. In the radio bands we find progressive delays of the most prominent light curve maxima with decreasing frequency, as expected from the frequency dependence of the $\tau =1$ surface of synchrotron self-absorption. The global maximum in the 86 GHz light curve becomes less prominent at lower frequencies, while a local maximum, appearing in 2014, strengthens toward decreasing frequencies, becoming pronounced at $\sim 5$ GHz. These tendencies suggest different Doppler boosting of stratified radio-emitting zones in the jet.

21 pages, 18 figures, accepted for publication in MNRAS

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Cited by in corpus (28)

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• Polarimetric Properties of Blazars Caught by the WEBT
• Repeated patterns of gamma-ray flares suggest structured jets of blazars as likely neutrino sources
• Emission Line Variability during a Nonthermal Outburst in the Gamma-Ray Bright Quasar 1156+295
• Multiwavelength variability of the blazar AO 0235+164
• On the Origin of Gamma-ray Flares from Bright Fermi Blazars
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• Multi-band Cross-correlated Radio Variability of the Blazar 3C 279
• X-ray Studies of Blazar 1ES 1959+650 Using SWIFT & XMM-NEWTON Satellite
• Correlation between emission-line luminosity and gamma-ray dominance in the blazar 3C 279
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• Understanding the Broadband Emission Process of 3C 279 through Longterm Spectral Analysis
• Multiband optical variability on diverse timescales of the blazar Ton 599 from 2011 to 2023
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• Testing Weak Equivalence Principle with IceCube Event and Blazar