We collect a sample of 51 Fermi-detected gamma-ray loud blazars with known radio Doppler factors and study properties of the Doppler factors of blazars at optical,X-ray and gamma-ray bands.A basic assumption is that the emission from the radio to gamma-ray bands of the blazars are produced by the nonthermal radiation of accelerated particles in a jet.Our results show that (1) the Doppler factors of blazars are a function of frequency,with the Doppler factor decreasing with frequency from the radio to X-ray regions,and then increasing from the X-ray to γ-ray regions which are similar to results given by Zhang et al.,and (2) there are marginal correlations between the Doppler factors at radio and X-ray bands and the synchrotron peak frequency,and a strong correlation between the Doppler factor in the gamma-ray band and the synchrotron peak frequency,but no correlation in the optical band.
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