Radio-loud and radio-quiet quasars observed by EXOSAT

Abstract

We present results from the spectral analysis of EXOSAT data on 31 quasars, 18 radio-loud and 13 radio-quiet. Simple power-law models with fixed (Galactic) absorption give acceptable fits to the spectra obtained in the 2–10 keV band. Using the results from these fits we have compared the distributions of spectral indices α for the radio-loud and radio-quiet quasars in the sample. We find that the X-ray spectrum is flatter for radio-loud quasars, $$\overline\alpha = 0.66\pm 0.07$$, and is consistent with a single power-law index for these objects. The radio-quiet group, however, shows a steeper average spectrum, $$\overline\alpha = 0.90\pm 0.11$$, and a wider spread of indices.