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

• DOI: 10.1093/mnras/staa082
• Publication Date: 2020-01-10T20:10:26Z
• Authors: V M Larionov; S G Jorstad; A P Marscher; M Villata; C M Raiteri; P S Smith; I 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 I Carnerero; D Carosati; C Casadio; W-P Chen; G Damljanovic; A V Dementyev; A Di Paola; A Frasca; A Fuentes; J L Gómez; P Gónzalez-Morales; A Giunta; T S Grishina; M A Gurwell; V A Hagen-Thorn; T Hovatta; S Ibryamov; M Joshi; S Kiehlmann; J-Y Kim; G N Kimeridze; E N Kopatskaya; Yu A Kovalev; Y Y Kovalev; O M Kurtanidze; S O Kurtanidze; A Lähteenmäki; C Lázaro; L V Larionova; E G Larionova; G Leto; A Marchini; K Matsumoto; B Mihov; M Minev; M G Mingaliev; D Mirzaqulov; R V Muñoz 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 V Sotnikova; A Strigachev; C Thum; E Traianou; Yu V Troitskaya; I S Troitsky; P G Tsybulev; A A Vasilyev; O Vince; Z R Weaver; K E Williamson; G V Zhekanis
• Keywords: LINE ARRAY OBSERVATIONS; Method; Spectroscopic; polarimetric [Techniques]; 01 natural sciences; 7. Clean energy; spectroscopic [Techniques]; techniques: photometric; Methods: observational; Methods; quasars: individual: 3C 279; Observational; Quasar; Quasars: individual: 3C 279; High Energy Astrophysical Phenomena (astro-ph.HE); HIGH-FREQUENCIES; Galaxies: active; 520; 3C 279; Astronomy & astrophysics; Technique; BL LACERTAE OBJECTS; 3C 279; Active; Galaxies; Individual; Methods; Observational; Photometric; Polarimetric; Quasars; Spectroscopic; Techniques; Techniques; Techniques; methods: observational; Astrophysics - High Energy Astrophysical Phenomena; ACTIVE GALACTIC NUCLEI; active [Galaxies]; Active; galaxies: active; Techniques: spectroscopic; FOS: Physical sciences; Individual; Photometric; 530; MILLIMETER WAVELENGTHS; Galaxie; EGRET-DETECTED QUASARS; individual: 3C 279 [Quasars]; SUPERLUMINAL MOTION; 0103 physical sciences; observational [Methods]; Quasars; Astronomical and space sciences; POLARIMETRIC OBSERVATIONS; XMM-NEWTON; ta115; photometric [Techniques]; Polarimetric; Techniques: polarimetric; Galaxies; Astrophysics - Astrophysics of Galaxies; Techniques; techniques: polarimetric; WEBT CAMPAIGN; 13. Climate action; Astrophysics of Galaxies (astro-ph.GA); Techniques: photometric; techniques: spectroscopic

ABSTRACT 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 $\gtrsim 3$ 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.