Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: MHD Simulations of Accretion onto Sgr A*: Quiescent Fluctuations,
  Outbursts, and Quasi-Periodicity   High resolution observations of Sgr A* have revealed a wide variety of
phenomena, ranging from intense rapid flares to quasi-periodic oscillations,
making this object an ideal system to study the properties of low luminosity
accreting black holes. In this paper, we use a pseudo-spectral algorithm to
construct and evolve a three-dimensional magnetohydrodynamic model of the
accretion disk in Sgr A*. Assuming a hybrid thermal-nonthermal emission scheme,
we show that the MHD turbulence can by itself only produce factor of two
fluctuations in luminosity. These amplitudes in variation cannot explain the
magnitude of flares observed in this system. However, we also demonstrate that
density perturbations in the disk do produce outbursts qualitatively similar to
those observed by XMM-Newton in X-rays and ground-based facilities in the near
infrared. Quasi-periodic oscillations emerge naturally in the simulated
lightcurves. We attribute these to non-axisymmetric density perturbations that
emerge as the disk evolves back toward its quiescent state.

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The categories of this paper are: cs
0
The categories of this paper are: hep-ph
14
The categories of this paper are: math-ph
32
The categories of this paper are: atom-ph
26
The categories of this paper are: bayes-an
4
The categories of this paper are: cond-mat
20
The categories of this paper are: acc-phys
27
The categories of this paper are: comp-gas
22
The categories of this paper are: chao-dyn
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The categories of this paper are: hep-lat
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The categories of this paper are: hep-ex
29
The categories of this paper are: funct-an
10
The categories of this paper are: q-bio
31
The categories of this paper are: ao-sci
37
The categories of this paper are: supr-con
15
The categories of this paper are: nucl-ex