The STRUCTURE AND EMISSION MODEL OF THE RELATIVISTIC JET IN THE QUASAR 3C 279 INFERRED FROM RADIO TO HIGH-ENERGY Γ-Ray OBSERVATIONS IN 2008-2010

Abstract

We present time-resolved broad-band observations of the quasar 3C 279 obtained from multiwavelength campaigns conducted during the first two years of the Fermi Gamma-ray Space Telescope mission. While investigating the previously reported γ-ray/optical flare accompanied by a change in optical polarization, we found that the optical emission appears delayed with respect to the γ-ray emission by about 10 days. X-ray observations reveal a pair of 'isolated' flares separated by ∼ 90 days, with only weak γ-ray/optical counterparts. The spectral structure measured by Spitzer reveals a synchrotron component peaking in the mid-infrared band with a sharp break at the far-infrared band during the γ-ray flare, while the peak appears in the mm/sub-mm band in the low state. Selected spectral energy distributions are fitted with leptonic models including Comptonization of external radiation produced in a dusty torus or the broad-line region. Adopting the interpretation of the polarization swing involving propagation of the emitting region along a curved trajectory, we can explain the evolution of the broad-band spectra during the γ-ray flaring event by a shift of its location from ∼ 1 pc to ∼ 4 pc from the central black hole. On the other hand, if the γ-ray flare is generated instead at sub-pc distance from the central black hole, the far-infrared break can be explained by synchrotron self-absorption. We also model the low spectral state, dominated by the mm/sub-mm peaking synchrotron component, and suggest that the corresponding inverse-Compton component explains the steady X-ray emission.

Erratic Flaring of Bl Lac in 2012–2013: Multiwavelength Observations

“…All four objects show a flattening of the SED at wavelengths between 500 and 70 microns (this paper and Hayashida et al 2012;Nalewajko et al 2012;Wehrle et al 2012b). The flattening indicates the presence of a persistent component (presumably the core) and other more evanescent components, some of which may be identified on mm band VLBA images, and all of which are variable.…”

Modelling the multi-wavelength emission of flat-spectrum radio quasar 3C 279

“…The external radiation field energy densities in the jet comoving frame as function of the distance r along the jet are approximated by formulae (Hayashida et al 2012):…”

“…The external radiation fields in the jet comoving frame by Maxwellian distribution peaked at photon energies EBLR ∼ 10 eV × Γ and EIR ∼ 0.3 eV × Γ. In our calculation, we adopt the radiation density profile βBLR = 3 (Sikora et al 2009) and βIR = 4 (Hayashida et al 2012), respectively. Because the initial γ-ray emission site that is defined by x = 0 in the model does not show the real distance between the core and base of jet, we introduce another parameter LB to describe it in the fluid frame.…”

“…Multi-wavelength snapshot observations for several epoches including γ-rays show that the SED could be explained by the leptonic model (Hartman et al 2001). In order to comprehend intensively the energy spectrum character of the source, a multi-wavelength quasisimultaneous observation campaign has been organized by Hayashida et al (2012). Now that the aim of the present work is to study in more detail the jet structure and emission properties of 3C 279 in the steady state.…”

“…Given that the model parameter L and B0 dominate on the energy range of flat/reversed radio spectrum (Potter & Cotter 2012), we attempt to determine the length and magnetic of jet through the observed radio data. In order to do that, in Figure 1, we first calculate the radio differential flux spectra with different length of jet L. For comparison, the observed radio data of 3C 279 at two quiescent epoches (Hayashida et al 2012) are also shown in Figure 1 (blank and solid circle). It can be seen that (1) a flat radio spectrum is largely insensitive to the length of jet, and that it mainly affects the extend of the flat radio spectrum to low frequencies; (2) the observation of a flat/reversed radio spectrum is reproduced quite well with the length of the jet L ∼ 100 pc for the source; (3) the energy of departure from the flat/reversed spectrum locates on around ∼ 10 −4 eV.…”