SIMBAD references

The ROSAT All-Sky Survey observations of the complete hard X-ray selected Piccinotti AGN sample demonstrate that the soft X-ray spectra of almost none of the sample AGN can be simply represented by the power law extrapolated from the 2-10keV range. A comparison of the soft X-ray spectra of the sample members with their medium energy continua measured with HEAO-1 and EXOSAT revealed that about half of the AGN in the sample are inrinsically absorbed. Furthermore, almost all sample AGN show excess fluxes in their soft X-ray emission. These features in the spectra of active galactic nuclei have an important impact on the interpretation of the cosmic soft X-ray background.