Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Optical Counterparts of X-Ray Point Sources Observed by CHANDRA in
  NGC5128: 20 New Globular Cluster X-Ray Sources   VLT images in $BVI$ are used to identify the optical counterparts to bright
CHANDRA X-ray points sources discovered by Kraft et al. (2001, ApJ, 560, 675)
in NGC5128. Of a total of 111 X-ray point sources with L_X>2*10^{36} ergs/s
present in a 56 arcmin^2 field centered on this galaxy, 58 have optical
counterparts. Based on the sizes, optical magnitudes and colors, 20 new
globular cluster counterparts of X-ray sources are identified, plus 3
identified based on their sizes. This brings the total number of globular
cluster X-ray sources in this galaxy to 33, and establishes that 30% of the
X-ray point sources in NGC5128 are associated with globular clusters. These
X-ray globular clusters occupy the brightest end of the globular cluster
luminosity function, indicating that bright low-mass X-ray binaries are
preferentially found in massive clusters. Most of the globular clusters with
X-ray sources have red colors, with 1.0<V-I<1.5, indicating that low-mass X-ray
binaries are preferentially formed in metal-rich clusters. The NGC5128 X-ray
globular cluster sources are brighter in comparison with the Milky Way sources:
there are 24 globular clusters with X-ray sources of L_x>10^{37} erg/sec. There
is, however, no globular cluster X-ray source in NGC5128 as bright as expected
for an accreting black hole. In addition, 31 optical counterparts of X-ray
point sources that are not associated with globular clusters are identified.
Finally, 53 X-ray point sources (48% of the population), do not have any
optical counterparts down to the faintest magnitude limits (B=25).

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The categories of this paper are: comp-gas
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The categories of this paper are: hep-th
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The categories of this paper are: gr-qc
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The categories of this paper are: ao-sci
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The categories of this paper are: quant-ph
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The categories of this paper are: chem-ph
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The categories of this paper are: nlin
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The categories of this paper are: econ
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The categories of this paper are: patt-sol
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The categories of this paper are: adap-org
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The categories of this paper are: cs
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The categories of this paper are: hep-lat
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The categories of this paper are: atom-ph
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The categories of this paper are: q-alg
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The categories of this paper are: hep-ex
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The categories of this paper are: bayes-an