NASA/IPAC EXTRAGALACTIC DATABASE
Date and Time of the Query: 2019-06-18 T08:35:50 PDT
Help | Comment | NED Home

For refcode 2008MNRAS.383.1501M:
Retrieve 47 NED objects in this reference.
Please click here for ADS abstract

NED Abstract

Copyright by Royal Astronomical Society. 2008MNRAS.383.1501M High-energy X-ray spectra of Seyferts and Unification schemes for active galactic nuclei Matthew Middleton, Chris Done and Nick Schurch Abstract. The Unified Model of active galactic nuclei (AGN) predicts that the sole difference between type 1 and 2 Seyfert galaxies nuclei is the viewing angle with respect to an obscuring structure around the nucleus. High-energy photons above 20 keV are not affected by this absorption if the column is Compton thin, so their 30-100 keV spectra should be the same. However, the observed spectra at high energies appear to show a systematic difference, with type 1 Seyfert galaxies having {GAMMA} ~ 2.1 whereas type 2 Seyfert galaxies are harder with {GAMMA} ~ 1.9. We estimate the mass and the accretion rate of Seyferts detected in these high-energy samples, and show that they span a wide range in L/L_Edd_. Both black hole binary systems and AGN show a correlation between spectral softness and Eddington fraction, so these samples are probably heterogeneous, spanning a range of intrinsic spectral indices which are hidden in individual objects by poor signal-to-noise ratio. However, the mean Eddington fraction for the type 1 Seyfert galaxies is higher than for the type 2 Seyfert galaxies, so the samples are consistent with this being the origin of the softer spectra seen in type 1 Seyfert galaxies. We stress that high-energy spectra alone are not necessarily a clean test of Unification schemes, but that the intrinsic nuclear properties should also change with L/L_Edd_. Key words: accretion, accretion discs, black hole physics, Galaxies: Seyfert
Retrieve 47 NED objects in this reference.
Please click here for ADS abstract

Back to NED Home