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Astron. Astrophys. 320, 696-704 (1997)

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The Piccinotti AGN sample observed in the ROSAT All-Sky Survey

N. Schartel 1, 2, 3, M. Schmidt 4, H.H. Fink 3, G. Hasinger 5 and J. Trümper 3

1 ESA, IUE Observatory, Vilspa, P.O.Box 50727,E-28080 Madrid, Spain
2 Affiliated to the Astrophysics Division, Space Science Department, ESTEC
3 Max-Planck-Institut für extraterrestrische Physik, D-85748 Garching, Germany
4 California Institute of Technology, Henry M. Robinson Lab of Astrophysics, Pasadena, California 91125, USA
5 Astrophysikalisches Institut Potsdam, An der Sternwarte 16, D-14482 Potsdam, Germany

Received 11 June 1996 / Accepted 5 September 1996


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 - 10 keV 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.

Key words: galaxies: active – galaxies: Seyfert – galaxies: quasars – X-rays: galaxies

Send offprint requests to: N. Schartel

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© European Southern Observatory (ESO) 1997

Online publication: June 30, 1998