Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A fit to the simultaneous broadband spectrum of Cygnus X-1 using the
  transition disk model   We have used the transition disk model to fit the simultaneous broad band
($2-500$ keV) spectrum of Cygnus X-1 from OSSE and Ginga observations. In this
model, the spectrum is produced by saturated Comptonization within the inner
region of the accretion disk, where the temperature varies rapidly with radius.
In an earlier attempt, we demonstrated the viability of this model by fitting
the data from EXOSAT, XMPC balloon and OSSE observations, though these were not
made simultaneously. Since the source is known to be variable, however, the
results of this fit were not conclusive. In addition, since only once set of
observations was used, the good agreement with the data could have been a
chance occurrence. Here, we improve considerably upon our earlier analysis by
considering four sets of simultaneous observations of Cygnus X-1, using an
empirical model to obtain the disk temperature profile. The vertical structure
is then obtained using this profile and we show that the analysis is self-
consistent. We demonstrate conclusively that the transition disk spectrum is a
better fit to the observations than that predicted by the soft photon
Comptonization model. Since the temperature profile is obtained by fitting the
data, the unknown viscosity mechanism need not be specified. The disk structure
can then be used to infer the viscosity parameter $\alpha$, which appears to
vary with radius and luminosity. This behavior can be understood if $\alpha$
depends intrinsically on the local parameters such as density, height and
temperature. However, due to uncertainties in the radiative transfer,
quantitative statements regarding the variation of $\alpha$ cannot yet be made.

14
The categories of this paper are: math-ph
21
The categories of this paper are: adap-org
32
The categories of this paper are: atom-ph
29
The categories of this paper are: funct-an
35
The categories of this paper are: mtrl-th
31
The categories of this paper are: ao-sci
4
The categories of this paper are: cond-mat
10
The categories of this paper are: q-bio
20
The categories of this paper are: acc-phys
34
The categories of this paper are: chem-ph
26
The categories of this paper are: bayes-an
15
The categories of this paper are: nucl-ex
11
The categories of this paper are: hep-lat
2
The categories of this paper are: math
1
The categories of this paper are: cs
30
The categories of this paper are: q-alg