Query : 2001A&A...375..155R

2001A&A...375..155R - Astronomy and Astrophysics, volume 375, 155-160 (2001/8-3)

Orbital Comptonization in accretion disks around black holes.


Abstract (from CDS):

We have performed Monte Carlo simulations of Compton upscattering of low-energy photons in an accretion disk around a Schwarzschild black hole. The photons gain energy from the rotational motion of the electrons in the disk. The upscattering occurs near the black hole horizon, where the flow velocity of the electrons approaches the speed of light. We show that this type of bulk-flow Comptonization can produce power-law X-ray spectra similar to the ones observed in black-hole X-ray transients in the high/soft state, i.e., a soft bump dominating the spectrum below ∼10keV and a power-law tail with photon index in the range 2-3. In order to reproduce the observed hard to soft flux ratio the disk has to have vertical optical depth above ∼3 at the last stable orbit. We conclude that the power-law component of the high/soft state of black-hole transients may be due to an intrinsically cool disk extending all the way to the hole, without a separate hot plasma component.

Abstract Copyright:

Journal keyword(s): accretion, accretion disks - black hole physics - radiation mechanisms: non-thermal - methods: statistical - X-rays: stars

Simbad objects: 3

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Number of rows : 3
N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2022
1 V* V1033 Sco HXB 16 54 00.137 -39 50 44.90   15.20 14.2 16.14   F5IV 1793 1
2 Granat 1915+105 HXB 19 15 11.55576 +10 56 44.9052           ~ 2454 0
3 HD 226868 HXB 19 58 21.6757355952 +35 12 05.784512688 9.38 9.72 8.91 8.42   O9.7Iabpvar 4122 0

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