Astronomy and Astrophysics – Astrophysics
Scientific paper
2000-06-16
Mon.Not.Roy.Astron.Soc. 321 (2001) 759
Astronomy and Astrophysics
Astrophysics
8 pages; accepted for publication in MNRAS; replaced with accepted version
Scientific paper
10.1046/j.1365-8711.2001.04056.x
Two component X-ray spectra (soft multicolor black body plus harder power law) are frequently observed from accreting black holes. These components are presumably associated with the different parts of the accretion flow (optically thick and optically thin respectively) in the vicinity of the compact source. Most of the aperiodic variability of the X-ray flux on the short time scales is associated with the harder component. We suggest that drastically different amplitudes of variability of these two components are simply related to the very different viscous time scales in the geometrically thin and geometrically thick parts of the accretion flow. In the geometrically thin disks variations of viscosity or mass accretion rate occurring at large radius from the black hole on the local dynamical or thermal time scales do not cause any significant variations of the mass accretion rate at smaller radii due to a very long diffusion time. Any variations on the time scales shorter than the diffusion time scale are effectively dampened. On the contrary such variations can easily survive in the geometrically thick flows and as a result the mass accretion rate in the innermost region of the flow will reflect modulations of the mass accretion rate added to the flow at any distance from the black hole. Therefore if primary instabilities operate on the short time scales then the stability of the soft component (originating from the geometrically thin and optically thick flow) and variability of the hard component (coming from the geometrically thick and optically thin flow) are naturally explained.
Churazov Eugene
Gilfanov Marat
Revnivtsev Mike
No associations
LandOfFree
Soft state of Cygnus X-1: stable disk and unstable corona does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Soft state of Cygnus X-1: stable disk and unstable corona, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Soft state of Cygnus X-1: stable disk and unstable corona will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-655725