ROSAT Observations of Blazars from a Polarized Radio-selected Sample

We have observed with ROSAT six blazars from the sample of 31 polarized objects constructed by Impey & Tapia (1988). Results of the spectral analysis in the ROSAT band of three objects, PKS 0301 -243, PKS 1055+018, and PG 1424+240 are presented here and compared with the three previously published objects. Using a simple power-law model with free absorption a wide range of spectral slopes is found, from 0.2 to 2.2 in the energy spectral index α_x_. Objects with emission lines have flatter X-ray spectra than lineless objects. Indication of spectral curvature within the X-ray band is found in the sense of a concavity (soft excess) for the flattest spectrum and a convexity (soft deficiency) for the steepest one. The X-ray spectral shape is discussed in relation to the overall energy distribution for the six objects. The results are compared with other samples of blazars. The X-ray spectral index, α_x_, is found to be anticorrelated with the broadband spectral index α_RO_ and with bolometric luminosity and redshift. It is suggested that the different spectra of quasar-like and BL Lac-like blazars represent extremes in a continuous distribution rather than two distinct populations.