The optical/UV bump seen in quasars is often modeled as the integrated thermal emission from an optically thick, geometrically thin accretion disk around a supermassive black hole. Soft X-ray excesses recently detected in optically selected (PG) quasars have consequently been attributed to the hot tail of the accretion disk spectrum. However, the high temperatures and luminosities inferred favor a picture in which supercritical, radiation-supported tori around 10^7^-10^8^ M_sun_ black holes are responsible for the UV/soft X-ray thermal component. We investigate models of thick accretion disks and, in particular, the effects of the toroidal shape on the observed thermal emission. The occultation of the innermost disk region due to self-shadowing and the reflection effect of photons off the funnel walls are taken into account. The dependence of the observed spectrum on the viewing angle is discussed. It is suggested that high- and low-inclination systems are responsible for the optical/UV and UV/soft X-ray excesses, respectively.

Madau, P. (1988). Thick accretion disks around black holes and the UV/soft X-ray excess in quasars. THE ASTROPHYSICAL JOURNAL, 327(1 Part 1), 116-127 [10.1086/166175].

Thick accretion disks around black holes and the UV/soft X-ray excess in quasars

Madau, P
1988

Abstract

The optical/UV bump seen in quasars is often modeled as the integrated thermal emission from an optically thick, geometrically thin accretion disk around a supermassive black hole. Soft X-ray excesses recently detected in optically selected (PG) quasars have consequently been attributed to the hot tail of the accretion disk spectrum. However, the high temperatures and luminosities inferred favor a picture in which supercritical, radiation-supported tori around 10^7^-10^8^ M_sun_ black holes are responsible for the UV/soft X-ray thermal component. We investigate models of thick accretion disks and, in particular, the effects of the toroidal shape on the observed thermal emission. The occultation of the innermost disk region due to self-shadowing and the reflection effect of photons off the funnel walls are taken into account. The dependence of the observed spectrum on the viewing angle is discussed. It is suggested that high- and low-inclination systems are responsible for the optical/UV and UV/soft X-ray excesses, respectively.
Articolo in rivista - Articolo scientifico
Accretion Disks; Black Holes (Astronomy); Quasars; Thermal Emission; Ultraviolet Radiation; X Ray Sources; Active Galactic Nuclei; Angular Momentum; Black Body Radiation; Computational Astrophysics; Seyfert Galaxies; Astrophysics; BLACK HOLES; QUASARS; RADIATION MECHANISMS; STARS: ACCRETION
English
1988
327
1 Part 1
116
127
none
Madau, P. (1988). Thick accretion disks around black holes and the UV/soft X-ray excess in quasars. THE ASTROPHYSICAL JOURNAL, 327(1 Part 1), 116-127 [10.1086/166175].
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/10281/453444
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