Issue A&A Volume 387, Number 3, June I 2002 Page(s) 918 - 930 Section Formation, structure and evolution of stars DOI http://dx.doi.org/10.1051/0004-6361:20020294

A&A 387, 918-930 (2002)
DOI: 10.1051/0004-6361:20020294

The transition from a cool disk to an ion supported flow

H. C. Spruit and B. Deufel

Max-Planck-Institut für Astrophysik, Postfach 1317, 85741 Garching, Germany

(Received 31 August 2001 / Accepted 26 February 2002 )

Abstract
We show that the inner regions of a cool accretion disk in an X-ray binary can transform into an advective, ion supported accretion flow (an optically thin ADAF, here called ISAF), through events involving only the known properties of the Coulomb interaction in a two-temperature plasma, standard radiation processes, and viscous heating. The optically thin inner edge of the disk is heated to a few 100 keV by the strong flux of hot ions from the surrounding hot ISAF. We show that he resident ions in this "warm" disk are thermally unstable due to internal viscous heating, and heat up to their virial temperature. The innermost disk regions thus evaporate and feed the ISAF. These processes are demonstrated with time dependent calculations of a two-temperature plasma in vertical hydrostatic equilibrium, including heating by external ions, internal proton-electron energy exchange, and viscous heating. The process complements the "coronal" evaporation mechanism which operates at larger distances from the central object.

Key words: accretion, accretion disks -- X-rays: binaries -- black hole physics -- radiations mechanisms: general, radiative transfer

Offprint request: H. C. Spruit, henk@mpa-garching.mpg.de

SIMBAD Objects

© ESO 2002

What is OpenURL?