Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Statistical Analysis of Point-like Sources in Chandra Galactic Center
  Survey   {\it Chandra} Galactic Center Survey detected $\sim 800$ X-ray point-like
sources in the $2^{\circ} \times 0.8^{\circ}$ sky region around the Galactic
Center. In this paper, we study the spatial and luminosity distributions of
these sources according to their spectral properties. Fourteen bright sources
detected are used to fit jointly an absorbed power-law model, from which the
power-law photon index is determined to be $\sim$2.5. Assuming that all other
sources have the same power-law form, the relation between hardness ratio and
HI column density $N_H$ is used to estimate the $N_H$ values for all sources.
Monte Carlo simulations show that these sources are more likely concentrated in
the Galactic center region, rather than distributed throughout the Galactic
disk. We also find that the luminosities of the sources are positively
correlated with their HI column densities, i.e. a more luminous source has a
higher HI column density. From this relation, we suggest that the X-ray
luminosity comes from the interaction between an isolated old neutron star and
interstellar medium (mainly dense molecular clouds). Using the standard Bondi
accretion theory and the statistical information of molecular clouds in the
Galactic center, we confirm this positive correlation and calculate the
luminosity range in this scenario, which is consistent with the observation
($10^{32}\sim 10^{35}$ ergs s$^{-1}$).

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The categories of this paper are: atom-ph
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The categories of this paper are: math-ph
11
The categories of this paper are: hep-lat
21
The categories of this paper are: adap-org
3
The categories of this paper are: physics
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The categories of this paper are: dg-ga
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The categories of this paper are: ao-sci
7
The categories of this paper are: hep-th
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The categories of this paper are: alg-geom
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The categories of this paper are: acc-phys
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The categories of this paper are: bayes-an
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The categories of this paper are: hep-ph
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The categories of this paper are: cond-mat
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The categories of this paper are: hep-ex
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The categories of this paper are: supr-con
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The categories of this paper are: eess