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Soft state of Cygnus X-1: stable disc and unstable corona

2001; Oxford University Press; Volume: 321; Issue: 4 Linguagem: Inglês

10.1046/j.1365-8711.2001.04056.x

1365-2966

E. Churazov, M. Gilfanov, M. Revnivtsev,

Astrophysics and Cosmic Phenomena

Two-component X-ray spectra (soft multicolour black-body and 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.