Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Compact and Diffuse Sources in the Galactic Center Region   The 10 by 10 degrees region around dynamic center of our Galaxy is known to
host a large number of bright X-ray sources, most of which are low mass binary
systems. While high luminosity Z-sources are especially bright in the standard
X-ray band (e.g. 2-10 keV), lower luminosity systems are dominating the flux
above 30 keV. The two hardest sources in the region, i.e. 1E1740.7-2942 and GRS
1758-258 are thought to be black hole candidates (BHC) based on the similarity
of spectral properties and short-term variability to that of dynamically proven
BHCs. However, while most of the other galactic BHCs are known to be
transients, these two objects could be considered persistent though variable
sources. The persistent behavior of these sources implies some constraints on
the parameters of the binary systems. Both sources were detected in the first
GRANAT observation of the GC region. They are the only two persistent BHCs seen
in the 35-75 keV SIGMA image after collecting several million seconds of
exposure time over eight years, indicating that they are perhaps the only two
persistent BHCs in the region.
  Another peculiar object in the field is of course a putative supermassive
black hole (Sgr A*) at the dynamic center of our Galaxy. The present day's
X-ray luminosity from Sgr A* is very small ($\la 10^{36}$ erg/s). However an
indication that Sgr A* might have been much brighter in the past was found
while studying diffuse X-ray emission in the region. We speculate here on how
future X-ray observatories may verify the hypothesis of the violent activity of
Sgr A* in the past.

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The categories of this paper are: hep-th
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The categories of this paper are: nucl-ex
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The categories of this paper are: patt-sol
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The categories of this paper are: hep-lat
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The categories of this paper are: math
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The categories of this paper are: cmp-lg
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The categories of this paper are: nucl-th
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The categories of this paper are: q-fin
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The categories of this paper are: stat
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The categories of this paper are: dg-ga
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The categories of this paper are: math-ph
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The categories of this paper are: plasm-ph
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The categories of this paper are: cs
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The categories of this paper are: gr-qc
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The categories of this paper are: adap-org
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The categories of this paper are: mtrl-th