Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Modeling the response of a standard accretion disc to stochastic viscous
  fluctuations   The observed variability of X-ray binaries over a wide range of time-scales
can be understood in the framework of a stochastic propagation model, where
viscous fluctuations at different radii induce accretion rate variability that
propagate inwards to the X-ray producing region. The scenario successfully
explains the power spectra, the linear rms-flux relation as well as the
time-lag between different energy photons. The predictions of this model have
been obtained using approximate analytical solutions or empirically motivated
models which take into account the effect of these propagating variability on
the radiative process of complex accretion flows. Here, we study the variation
of the accretion rate due to such viscous fluctuations using a hydro-dynamical
code for the standard geometrically thin, gas pressure dominated $\alpha$-disc
with a zero torque boundary condition. Our results confirm earlier findings
that the time-lag between a perturbation and the resultant inner accretion rate
variation depends on the frequency (or time-period) of the perturbation. Here
we have quantified that the time-lag $t_{lag} \propto f^{-0.54}$, for
time-periods less than the viscous time-scale of the perturbation radius and is
nearly constant otherwise. This, coupled with radiative process would produce
the observed frequency dependent time-lag between different energy bands. We
also confirm that if there are random Gaussian fluctuations of the
$\alpha$-parameter at different radii, the resultant inner accretion rate has a
power spectrum which is a power-law.

18
The categories of this paper are: econ
36
The categories of this paper are: cmp-lg
26
The categories of this paper are: bayes-an
33
The categories of this paper are: plasm-ph
5
The categories of this paper are: gr-qc
21
The categories of this paper are: adap-org
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The categories of this paper are: q-fin
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The categories of this paper are: chem-ph
22
The categories of this paper are: chao-dyn
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The categories of this paper are: q-alg
20
The categories of this paper are: acc-phys
3
The categories of this paper are: physics
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The categories of this paper are: solv-int
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The categories of this paper are: hep-lat
0
The categories of this paper are: hep-ph
2
The categories of this paper are: math