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bmc: Comptonization by relativistic matter
This is an analytic model describing Comptonization of soft photons by matter undergoing relativistic bulk-motion. The typical scenario involves thermal X-rays from the inner region of an accretion disk in a black-hole binary illuminating in-falling matter in close proximity to the black-hole event horizon.
For a detailed description of the model, refer to Titarchuk, Mastichiadis & Kylafis 1997, ApJ, 487, 834; Titarchuk & Zannias, 1998, ApJ, 493, 863; Laurent & Titarchuk 1999, ApJ, 511, 289; Borozdin, Revnivtsev, Trudolyubov, Shrader, & Titarchuk, 1999, ApJ, 517, 367; or Shrader & Titarchuk 1999, ApJ 521, L121.
The model parameters are the characteristic black-body temperature of
the soft photon source, a spectral (energy) index, and an illumination
parameter characterizing the fractional illumination of the
bulk-motion flow by the thermal photon source. It must be emphasized
that this model is not an additive combination of power law and
thermal sources, rather it represents a self-consistent
convolution. The bulk-motion up-scattering and Compton recoil combine
to produce the hard spectral tail, which combined with the thermal
source results in the canonical high-soft-state spectrum of black hole
accretion. The position of the sharp high energy cutoff (due to
recoil) can be determined using the theta function
. The model can also be used for the general
Comptonization case when the energy range is limited from above by the
plasma temperature (see compTT and compST).
| par1 | Temperature of thermal photon source in keV. |
| par2 | Energy spectral index alpha. |
| par3 | Log of the  parameter. Note that f in Borozdin et al. 1999
and
Shrader & Titarchuk 1999
is
 |
| norm |  defined in Borozdin et al
1999
and Shrader & Titarchuk
(1999) |