Modelling the $\gamma$-ray variability of 3C 273
  We investigate MeV-GeV $\gamma$-ray outbursts in 3C 273 in the frame of a time-dependent one-zone synchrotron self-Compton (SSC) model. In this model, electrons are accelerated to extra-relativistic energy through the stochastic particle acceleration and evolve with the time, nonthermal photons are produced by both synchrotron and inverse Compton scattering of synchrotron photons. Moreover, nonthermal photons during a quiescent are produced by the relativistic electrons in the steady state and those during a outburst are produced by the electrons whose injection rate is changed at some time interval. We apply the model to two exceptionally luminous $\gamma$-ray outbursts observed by the Fermi-LAT from 3C 273 in September, 2009 and obtain the multi-wavelength spectra during the quiescent and during the outburst states, respectively. Our results show that the time-dependent properties of outbursts can be reproduced by adopting the appropriate injection rate function of the electron population. 
Y.G. Zheng (YNNU), L. Zhang (YNU), B.R. Huang (YNNU) and S.J. Kang   (HUST)
astro-ph.HE