Modelling the multi-wavelength emission of flat spectrum radio quasar 3C   279
  We employ a length-dependent conical jet model for the jet structure and emission properties of flat spectrum radio quasar 3C 279 in the steady state. In the model, ultra-relativistic leptons are injected at the base of jet and propagate along the jet structure, non-thermal photons are produced by both synchrotron emission and inverse Comtpon scattering off synchrotron photons and external soft photons at each segment of jet. We derive the total energy spectra contribution through integrating every segment. We apply the model to the quasi-simultaneous multi-wavelength observed data of two quiescent epoches. Using the observed radio data of source, we determine the length of jet $L\sim 100$ pc, and magnetic field $B_{0}\sim 0.1-1$ G at the base of jet. Assuming a steady geometry of the jet structure and suitable physical parameters, we reproduce the multi-wavelength spectra during two quiescent observed epoches, respectively. Our results show that the initial $\gamma$-ray emission site takes place at $\sim 0.5$ pc from black hole. 
Y.G. Zheng (YNNU) and C.Y. Yang (YNAO)
astro-ph.HE