  In this paper, we discuss the light-curve features of various flaring
scenarios in a time-dependent leptonic model for low-frequency-peaked blazars.
The quasar 3C273 is used as an illustrative example. Our code takes into
account Fermi-II acceleration and all relevant electron cooling terms,
including the external radiation fields generally found to be important in the
modeling of the SEDs of FSRQs, as well as synchrotron self absorption and
gamma-gamma pair-production. General parameters are constrained through a fit
to the average spectral energy distribution (SED) of the blazar by numerically
solving the time-dependent Fokker-Planck equation for the electron evolution in
a steady-state situation. We then apply perturbations to several input
parameters (magnetic field, particle injection luminosity, acceleration time
scale) to simulate flaring events and compute time-dependent SEDs and light
curves in representative energy bands (radio, optical, X-rays, gamma-rays).
Time lags between different bands are evaluated using a discrete cross
correlation analysis. We find that Fermi-II acceleration has a significant
effect on the distributions and that flaring events caused by increased
acceleration efficiency of the Fermi II process will produce a correlation
between the radio, optical and gamma-ray bandpasses, but an anti-correlation
between these three bandpasses and the X-ray band, with the X-rays lagging
behind the variations in other bands by up to several hours.
