Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A First Estimate Of The X-Ray Binary Frequency As A Function Of Star
  Cluster Mass In A Single Galactic System   We use the previously-identified 15 infrared star-cluster counterparts to
X-ray point sources in the interacting galaxies NGC 4038/4039 (the Antennae) to
study the relationship between total cluster mass and X-ray binary number. This
significant population of X-Ray/IR associations allows us to perform, for the
first time, a statistical study of X-ray point sources and their environments.
We define a quantity, \eta, relating the fraction of X-ray sources per unit
mass as a function of cluster mass in the Antennae. We compute cluster mass by
fitting spectral evolutionary models to K_s luminosity. Considering that this
method depends on cluster age, we use four different age distributions to
explore the effects of cluster age on the value of \eta and find it varies by
less than a factor of four. We find a mean value of \eta for these different
distributions of \eta = 1.7 x 10^-8 M_\sun^-1 with \sigma_\eta = 1.2 x 10^-8
M_\sun^-1. Performing a \chi^2 test, we demonstrate \eta could exhibit a
positive slope, but that it depends on the assumed distribution in cluster
ages. While the estimated uncertainties in \eta are factors of a few, we
believe this is the first estimate made of this quantity to ``order of
magnitude'' accuracy. We also compare our findings to theoretical models of
open and globular cluster evolution, incorporating the X-ray binary fraction
per cluster.

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The categories of this paper are: q-bio
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The categories of this paper are: math
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The categories of this paper are: mtrl-th
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The categories of this paper are: cond-mat
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The categories of this paper are: q-fin
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The categories of this paper are: physics
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The categories of this paper are: nlin
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The categories of this paper are: hep-th
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The categories of this paper are: stat
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The categories of this paper are: funct-an
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The categories of this paper are: alg-geom
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The categories of this paper are: nucl-ex
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The categories of this paper are: chao-dyn
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The categories of this paper are: patt-sol
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The categories of this paper are: dg-ga
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The categories of this paper are: hep-ex