Summary.
Recent papers dealing with the most controversial aspects of AGNs are reviewed. They suggest interesting conclusions: all Seyferts can be described by a single parameter, the X-ray column density; radio loud AGNs may host a rapidly spinning black hole and radio quiet AGNs a slowly spinning black hole; high-ionization AGNs (Seyfert galaxies and QSOs) contain an optically thick, geometrically thin accretion disk, while low-ionization AGNs (Liners) contain an optically thin, geometrically thick accretion disk; a number of blazars have been classified as BLLs on the basis of insufficient data; most objects with weak broad emission lines are in fact HPQs; many objects have been called Liners although they are not AGNs but rather the result of stellar activity; type 2 QSOs exist, but are quite inconspicuous if radio quiet.
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Received 16 November 1999 / Published online: 15 February 2000
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Véron-Cetty, M., Véron, P. The emission line spectrum of active galactic nuclei and the unifying scheme. The Astron Astrophys Rev 10, 81–133 (2000). https://doi.org/10.1007/s001590000006
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DOI: https://doi.org/10.1007/s001590000006