Evaporation of accretion disks around black holes: the disk-corona transition and the connection to the ADAF

We apply the disk-corona evaporation model (Meyer & Meyer-Hofmeister 1994) originally derived for dwarf novae to black hole systems. This model describes the transition of a thin cool outer disk to a hot coronal flow. The mass accretion rate determines the location of this transition. For a number of well studied black hole binaries we take the mass flow rates derived from a fit of the ADAF model to the observed spectra (for a review see Narayan, Mahadevan, & Quataert 1999) and determine where the transition of accretion via a cool disk to a coronal flow/ADAF would be located for these rates. We compare with the observed location of the inner disk edge, as estimated from the maximum velocity of the Hα emission line. We find that the transition caused by evaporation agrees with this in stellar disks. We also show that the ADAF and the “thin outer disk + corona” are compatible in terms of the physics in the transition region. Subject headings: accretion, accretion disks—black hole physics—stars: binaries— galaxies: nuclei