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1987
Well before the discovery of quasars, a special class of galaxies was known to harbor unusually powerful nuclei (Seyfert, 1943). Two primary defining characteristics of these active galactic nuclei (AGNs) are an intense point-like nuclear continuum source and strong, broad emission lines, neither of which could arise from ordinary stellar processes ...
Matthew A. Malkan +2 more
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Well before the discovery of quasars, a special class of galaxies was known to harbor unusually powerful nuclei (Seyfert, 1943). Two primary defining characteristics of these active galactic nuclei (AGNs) are an intense point-like nuclear continuum source and strong, broad emission lines, neither of which could arise from ordinary stellar processes ...
Matthew A. Malkan +2 more
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The Masses of Active Galactic Nuclei
Vistas in Astronomy, 1988The study of the variability of the X-ray radiation in AGNs on time scales of 102 to 105sec is of fundamental importance for understanding the nature of their central source. Recently Wandel & Mushotzky [1] determined the masses of AGNs from their X-ray variability assuming the emitting region of X-rays to be five Schwarzschild radii.
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2021
Almost all galaxies host in their center a supermassive black hole of mass between a million and tens of billions solar masses. Supermassive black holes grow in symbiosis with their host galaxies across the Hubble time, occasionally accreting surround matter, giving rise to an Active Galactic Nuclei (AGN).
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Almost all galaxies host in their center a supermassive black hole of mass between a million and tens of billions solar masses. Supermassive black holes grow in symbiosis with their host galaxies across the Hubble time, occasionally accreting surround matter, giving rise to an Active Galactic Nuclei (AGN).
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2008
These lectures review briefly the spectra and classification of active galactic nuclei (AGN), including quasi-stellar objects (QSOs), and the properties of their ‘host’ galaxies; starbursts (SB) and the possible association between galaxy interactions, SB, and AGN.
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These lectures review briefly the spectra and classification of active galactic nuclei (AGN), including quasi-stellar objects (QSOs), and the properties of their ‘host’ galaxies; starbursts (SB) and the possible association between galaxy interactions, SB, and AGN.
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Active galactic nuclei in the ultraviolet
Astrophysics and Space Science, 2007The frontier for ultraviolet studies of active galactic nuclei is the time domain: in particular, reverberation mapping of the broad emission-line region can lead to determination of the geometry and kinematics of accretion flows and winds as well as accurate measurement of the masses of the central black holes.
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Ultrahigh-energy photons up to 1.4 petaelectronvolts from 12 γ-ray Galactic sources
Nature, 2021Zhen Cao, Felix Aharonian, Yiwei Bao
exaly
Phenomenology of Active Galactic Nuclei
1990Active galactic nuclei constitute a somewhat vaguely defined class of objects. It is very well possible that most galaxies have nuclei and that these are active in the sense that there is an energy source in addition to the thermonuclear sources inside the constituent stars.
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