  Some recent work has shown that the spectrum of Seyfert 1 Galaxies is very
similar to that of several Galactic Black Hole Candidates (GBHCs) in their hard
state. However, the smallness of the observed reflection component in Cygnus
X-1, in addition to other constraints, seem to rule out the two-phase model
(otherwise successful in the case of Seyfert Galaxies) for GBHCs. Here, we show
that the latter conclusion is based on a number of key assumptions that
probably are not valid when the overlying corona is patchy, e.g., when it is
comprised of localized magnetic flares above the disk. We show that in GBHCs
the energy deposited by the X-rays cannot be re-radiated fast enough to
maintain equilibrium, unless the X-ray skin heats up to the Compton
temperature, at which point the gas is mostly ionized. This leads to a
substantially reduced cooling rate for the active regions due to the
correspondingly smaller number of re-injected low-energy photons. We model this
effect by introducing a transition layer situated between the corona and the
cold disk, and find that the resulting spectrum is harder than that obtained
with the standard (and unrealistic) two-phase model. We apply this model to
Cygnus X-1 and show that it can account for its observed spectrum. This
analysis therefore seems to provide a consistentpicture for both Seyfert
Galaxies and GBHCs within the same framework, with differences arising due to
the changing physical conditionsin the two categories of sources, rather than
due to an ad hoc variation of the model parameters.
