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Astron. Astrophys. 361, L53-L56 (2000)


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Letter to the Editor

Truncated disks - advective tori; new solutions of accretion flows around black holes

A. Hujeirat and M. Camenzind

Landessternwarte-Koenigstuhl, 69117 Heidelberg, Germany

Received 31 July 2000 / Accepted 14 August 2000

Abstract

Our quasi-steady 2D numerical radiative hydrodynamical investigations of two-temperature accretion flows around black holes indicate that standard disks are thermally and hydrodynamically stable against transition to optically thin disks at large radii. Optically thin disks cool sufficiently rapid at large radii inducing a vertical collapse and forming thereby a standard disk which truncates close to the last stable orbit. In the absence of soft photons from the adjusting standard disk, we confirm the runaway cooling of the inner optically thin disk. This runaway however terminates if the radial flux of soft photons from the outer standard disk is taken into account. Instead, a cooling-driven front starts to propagates from outside-to-inside continuously extending the thick disk down to the very inner region where it terminates via an oppositely-oriented heating front that forms a hot advective and sub-keplerian torus.

The transition between the two configuration occurs where the ratio of the cooling to the heating time attains a minimum value. The transition is found to be rather sharp and gives rise to outwards-oriented motions of very hot plasma that enlarges the combined Compton-Synchrotron cooling regions considerably.

While the disk-torus configuration obtained depends weakly on whether the flow is a one or two-temperature plasma, one-temperature tori are hotter and fill larger volumes than their two-temperature counterparts.

Key words: black hole physics – accretion, accretion disks – hydrodynamics – radiation mechanisms: non-thermal

Send offprint requests to: A. Hujeirat

© European Southern Observatory (ESO) 2000

Online publication: October 10, 2000

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