Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Self-Consistent Thermal Accretion Disk Corona Models for Compact
  Objects: II. Application to Cygnus X-1   We apply our self-consistent accretion disk corona (ADC) model, with two
different geometries, to the broad-band X-ray spectrum of the black hole
candidate Cygnus X-1. As shown in a companion paper (Dove, Wilms, and
Begelman), models where the Comptonizing medium is a slab surrounding the cold
accretion disk cannot have a temperature higher than about 120 keV for optical
depths greater than 0.2, resulting in spectra that are much softer than the
observed 10-30 keV spectrum of Cyg X-1. In addition, the slab geometry models
predict a substantial ``soft excess'' at low energies, a feature not observed
for Cyg X-1, and Fe K\alpha fluorescence lines that are stronger than observed.
Previous Comptonization models in the literature invoke a slab geometry with
the optical depth \tau_T \gta 0.3 and the coronal temperature T_c \sim 150 keV,
but they are not self-consistent. Therefore, ADC models with a slab geometry
are not appropriate for explaining the X-ray spectrum of Cyg X-1. Models with a
spherical corona and an exterior disk, however, predict much higher
self-consistent coronal temperatures than the slab geometry models. The higher
coronal temperatures are due to the lower amount of reprocessing of coronal
radiation in the accretion disk, giving rise to a lower Compton cooling rate.
Therefore, for the sphere+disk geometry, the predicted spectrum can be hard
enough to describe the observed X-ray continuum of Cyg X-1 while predicting Fe
fluorescence lines having an equivalent width of \sim 40 eV. Our best-fit
parameter values for the sphere+disk geometry are \tau_T \approx 1.5 and T_c
\approx 90 keV.

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The categories of this paper are: hep-ex
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The categories of this paper are: math
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The categories of this paper are: nlin
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The categories of this paper are: eess
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The categories of this paper are: cond-mat
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The categories of this paper are: ao-sci
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The categories of this paper are: physics
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The categories of this paper are: adap-org
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The categories of this paper are: bayes-an
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The categories of this paper are: plasm-ph
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The categories of this paper are: hep-lat
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The categories of this paper are: hep-ph
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The categories of this paper are: stat
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The categories of this paper are: chao-dyn
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The categories of this paper are: solv-int
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The categories of this paper are: cs