A statistical study of XBLs, RBLs and FSRQs at 1.5 GHz

BL Lac objects are similar to theflat spectrumradioquasarsin manyaspects except regarding the emission lines. In order to study their relationship, we selected 56 BL Lacertae objects (33 X-ray-selected, 23 radio-selected) and 45 flat spectrum radio quasars, analyzed their radio luminosities and core-dominanceparameters. We found that the radio luminosities of the radio selected BL Lac objects located in between the X-ray selected BL Lac objects and the flat spectrum radio quasars. However, this intermediate position does not hold for the core-dominance parameter: the RBLs have the largest core-dominanceparameters. This sug- gests that the core-dominance parameter can not be taken as a sequencing criterion. We also investigatedthe correlationbetween the luminosity and the core-dominanceparameterfor the three subclasses. We concluded that, here, the sequence XBL-RBL—FSRQ still exists.