Multiwavelength behaviour of the blazar 3C 279: decade-long study from γ-ray to radio

V. M. Larionov, S. G. Jorstad, A. P. Marscher, M. Villata, C. M. Raiteri, P. S. Smith, Ivan Agudo, S. S. Savchenko, D. A. Morozova, J. A. Acosta-Pulido, M. F. Aller, H. D. Aller, T. S. Andreeva, A. A. Arkharov, R. Bachev, G. Bonnoli, G. A. Borman, V. Bozhilov, P. Calcidese, M. CarnereroD. Carosati, C. Casadio, W-P Chen, G. Damljanovic, A. Dementyev, A. Di Paola, A. Frasca, A. Fuentes, J. L. Gomez, P. Gonzalez-Morales, A. Giunta, T. S. Grishina, M. A. Gurwell, V. A. Hagen-Thorn, Talvikki Hovatta, S. Ibryamov, M. Joshi, S. Kiehlmann, J-Y Kim, Givi N. Kimeridze, E. N. Kopatskaya, Yu A. Kovalev, Y. Kovalev, O. M. Kurtanidze, Sofia O. Kurtanidze, Anne Lahteenmaki, C. Lazaro, L. Larionova, E. G. Larionova, G. Leto, A. Marchini, K. Matsumoto, B. Mihov, M. Minev, M. G. Mingaliev, D. Mirzaqulov, R. V. Munoz Dimitrova, I. Myserlis, A. A. Nikiforova, M. G. Nikolashvili, N. A. Nizhelsky, E. Ovcharov, L. D. Pressburger, I. A. Rakhimov, S. Righini, N. Rizzi, K. Sadakane, A. C. Sadun, M. R. Samal, R. Z. Sanchez, E. Semkov, S. G. Sergeev, L. A. Sigua, L. Slavcheva-Mihova, P. Sola, Yu Sotnikova, A. Strigachev, C. Thum, Efthalia Traianou, Yu Troitskaya, I. S. Troitsky, P. G. Tsybulev, A. A. Vasilyev, O. Vince, Z. R. Weaver, K. E. Williamson, G. Zhekanis

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We report the results of decade-long (2008-2018) γ -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 γ -ray light curves correlate well, with no delay ≳ 3 h, implying general cospatiality of the emission regions. The γ -ray-optical flux-flux relation changes with activity state, ranging from a linear to amore complex dependence. The behaviour of the Stokes parameters at optical and radio wavelengths, including 43 GHz Very Long Baseline Array 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 γ -ray variability on very short time-scales. The MgII 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 τ= 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 ∼5 GHz. These tendencies suggest different Doppler boosting of stratified radio-emitting zones in the jet.

Original languageEnglish
Pages (from-to)3829-3848
Number of pages20
JournalMonthly Notices of the Royal Astronomical Society
Issue number3
Publication statusPublished - 1 Mar 2020
MoE publication typeA1 Journal article-refereed


  • methods: observational
  • techniques: photometric
  • techniques: polarimetric
  • techniques: spectroscopic
  • galaxies: active
  • quasars: individual: 3C 279


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