The estimation of $\gamma$-ray Doppler factor for Fermi/LAT-detected
  blazars
  Blazars are a subclass of active galactic nuclei (AGNs) with extreme
observation properties, which is caused by the beaming effect, expressed by a
Doppler factor, in a relativistic jet. Doppler factor is an important parameter
in the blazars paradigm to indicate all of the observation properties, and many
methods were proposed to estimate its value. In this paper, we present a method
following Mattox et al. to calculate the lower limit on gamma-ray Doppler
factor for 809 selected Fermi/LAT-detected gamma-ray blazars by adopting the
available gamma-ray and X-ray data. Our sample included 342 flat-spectrum radio
quasars (FSRQs) and 467 BL Lac objects (BL Lacs), out of which 507 sources are
compiled with available radio core-dominance parameter (R) from our previous
study. Our calculation shows that the average values of the lower limit on
gamma-ray Doppler factor for FSRQs and BL Lacs are 6.87 and 4.31, respectively.
We compare and discuss our results with those from the literature. We found
that the derived lower limit on gamma-ray Doppler factor for some sources are
higher than that from the radio estimation, which could be possibly explained
by the jet bending within those blazars. Our results also suggest that the
gamma-ray and radio regions perhaps share the same relativistic effects. The
gamma-ray Doppler factor has been found to be correlated with both the
gamma-ray luminosity and core-dominance parameter, implying that the jet is
possibly continuous in the gamma-ray bands, and R is perhaps an indicator for a
beaming effect.
