Multiwavelength behaviour of the blazar 3C 279: decade-long study from γ-ray to radio
Larionov, V.M.; Jorstad, S.G.; Marscher, Alan P.; Villata, M.; Raiteri, C.M.; Smith, P.S.; Agudo, I.; Savchenko, S.S.; Morozova, D.A.; Acosta-Pulido, J.A.; Aller, M.F.; Aller, H.D.; Andreeva, T.S.; Arkharov, A.A.; Bachev, R.; Bonnoli, G.; Borman, G.A.; Bozhilov, V.; Calcidese, P.; Carnerero, M.I.; Carosati, D.; Casadio, C.; Chen, W.-P.; Damljanovic, G.; Dementyev, A.V.; Di Paola, A.; Frasca, A.; Fuentes, A.; Gómez, J.L.; Gónzalez-Morales, P.; Giunta, A.; Grishina, T.S.; Gurwell, M.A.; Hagen-Thorn, V.A.; Hovatta, T.; Ibryamov, S.; Joshi, M.; Kiehlmann, S.; Kim, J.-Y.; Kimeridze, G.N.; Kopatskaya, E.N.; Kovalev, Yu. A.; Kovalev, Y.Y.; Kurtanidze, O.M.; Kurtanidze, S.O.; Lähteenmäki, A.; Lázaro, C.; Larionova, L.V.; Larionova, E.G.; Leto, G.; Marchini, A.; Matsumoto, K.; Mihov, B.; Minev, M.; Mingaliev, M.G.; Mirzaqulov, D.; Muñoz Dimitrova, R.V.; Myserlis, I.; Nikiforova, A.A.; Nikolashvili, M.G.; Nizhelsky, N.A.; Ovcharov, E.; Pressburger, L.D.; Rakhimov, I.A.; Righini, S.; Rizzi, N.; Sadakane, K.; Sadun, A.C.; Samal, M.R.; Sanchez, R.Z.; Semkov, E.; Sergeev, S.G.; Sigua, L.A.; Slavcheva-Mihova, L.; Sola, P.; Sotnikova, Yu. V.; Strigachev, A.; Thum, C.; Traianou, E.; Troitskaya, Yu. V.; Troitsky, I.S.; Tsybulev, P.G.; Vasilyev, A.A.; Vince, O.; Weaver, Z.R.; Williamson, K.E.; Zhekanis, G.V.
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 a more 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 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 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.
↧