NASA/IPAC EXTRAGALACTIC DATABASE
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For refcode 1996MNRAS.282..493C:
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Copyright by Royal Astronomical Society. 1996MNRAS.282..493C Soft versus hard X-ray emission in active galactic nuclei: partial- covering and warm-plus-cold absorber models M. T. Ceballos and X. Barcons Instituto de Fisica de Cantabria (Consejo Superior de Investigaciones Cientificas - Universidad de Cantabria), 39005 Santander Spain Department de Fisica Moderna, Universidad de Cantabria, 39005 Santander, Spain Accepted 1996 April 15. Received 1996 April 10; in original form 1995 October 18 ABSTRACT We analyse the ROSAT Position Sensitive Proportional Counter (PSPC) hardness ratio and the 0.5-2-keV to 2-10-keV flux ratio of 65 active galactic nuclei (AGN) for which there are both ROSAT archival observations available and 2-10-keV fluxes, mostly from the HEAO-1 MC- LASS survey. We conclude that the simplest spectral model for the AGN that can accommodate the variety of X-ray colours obtained is a standard power law (with energy spectral index {alpha} ~ 0.9) plus a ~0.1-keV blackbody, both of which are partially absorbed. In our sample, type 1 AGN require an absorbing column around 10^22^ cm^-2^ with covering fractions between 20 and 100 per cent, while type 2 AGN display larger columns and ~100 per cent coverage. This simple model also provides a good link between soft and hard AGN X-ray luminosity functions and source counts. We also consider a warm absorber as an alternative model to partial covering and find that the presence of gas in two phases (ionized and neutral) is required. Key words: galaxies: active - galaxies: nuclei - X-rays: galaxies - X- rays: general.
Retrieve 65 NED objects in this reference.
Please click here for ADS abstract

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