Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: X-ray and Optical Study of Low Core Density Globular Clusters NGC6144
  and E3   We report on the Chandra X-ray Observatory and Hubble Space Telescope
observation of two low core density globular clusters, NGC6144 and E3. By
comparing the number of X-ray sources inside the half-mass radius to those
outside, we found 6 X-ray sources within the half-mass radius of NGC6144, among
which 4 are expected to be background sources; 3 X-ray sources are also found
within the half-mass radius of E3, of which 3 is expected to be background
source. Therefore, we cannot exclude that all our sources are background
sources. However, combining the results from X-ray and optical observations, we
found that 1-2 sources in NGC6144 and 1 source in E3 are likely to be
cataclysmic variables and that 1 source in NGC6144 is an active binary, based
on the X-ray and optical properties. The number of faint X-ray sources in
NGC6144 and E3 found with Chandra and HST is higher than a prediction based on
collision frequency, but is closer to that based on mass. Our observations
strongly suggest that the compact binary systems in NGC6144 and E3 are
primordial in origin.

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The categories of this paper are: eess
4
The categories of this paper are: cond-mat
36
The categories of this paper are: cmp-lg
29
The categories of this paper are: funct-an
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The categories of this paper are: bayes-an
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The categories of this paper are: chem-ph
0
The categories of this paper are: hep-ph
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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: gr-qc
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The categories of this paper are: hep-th
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The categories of this paper are: econ
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The categories of this paper are: q-alg
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The categories of this paper are: nucl-ex
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The categories of this paper are: physics
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The categories of this paper are: solv-int