BL Lac Objects and Unified Model

In this paper:1.The assumption of the dependence of Doppler factor on the emission frequency (δ_v≈δ₀(1/8)1og(v/v₀), Fan et al.1993, ApJ., 415, 113)is used to explain the observational differences between the radio-selected BL Lac objects (RBLs)and the X-Ray-Selected BL lac objects (XBLs):a)Hubble relation;b)dif ferent multiw aveleng th correlations;c)different regions in the effect ive spect ral index (αRO-αOX)diagram;d)different polarization.The results suggest that RBLs and XBLs are the same.2.From the analysis of the relation between infrared magnitude and redshift, it is proposed that the parent population of BLLac objects should be FRI radio galaxies and FRII(G)radio galaxies showing the optical spectra of a galaxy.3.From the superluminal motion, the assumption (δ_v≈δ₀(1/8)1og(v/v₀)is confirmed.4.Based on the relation between polarization and Doppler factor (Fan et al.1997a), it is proposed that the f, ratio of the beamed luminosity to the unbeamed luminosity in the sourceframe of OVVs/HPQs is smaller than that of BLLac objects:f_RBLs～6f_FSRQs.