Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Ultra-luminous X-ray Sources in nearby galaxies from ROSAT HRI
  observations I. data analysis   X-ray observations have revealed in other galaxies a class of extra-nuclear
X-ray point sources with X-ray luminosities of $10^{39}$--$10^{41}$ erg/sec,
exceeding the Eddington luminosity for stellar mass X-ray binaries. These
ultra-luminous X-ray sources (ULXs) may be powered by intermediate mass black
hole of a few thousand $M_\odot$ or stellar mass black holes with special
radiation processes. In this paper, we present a survey of ULXs in 313 nearby
galaxies with $D_{25}$$>$$1^\prime$ within 40 Mpc with 467 ROSAT HRI archival
observations. The HRI observations are reduced with uniform procedures, refined
by simulations that help define the point source detection algorithm employed
in this survey. A sample of 562 extragalactic X-ray point sources with $L_X =
10^{38}$--$10^{43}$ erg/sec is extracted from 173 survey galaxies, including
106 ULX candidates within the $D_{25}$ isophotes of 63 galaxies and 110 ULX
candidates between 1--2$\times D_{25}$ of 64 galaxies, from which a clean
sample of 109 ULXs is constructed to minimize the contamination from foreground
or background objects. In a subsequent paper, the statistic properties of the
survey will be studied to calculate the occurrence frequencies and luminosity
functions for ULXs in different types of galaxies to shed light on the nature
of these enigmatic sources.

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The categories of this paper are: plasm-ph
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The categories of this paper are: solv-int
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The categories of this paper are: cond-mat
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The categories of this paper are: nucl-th
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The categories of this paper are: hep-th
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The categories of this paper are: dg-ga
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The categories of this paper are: bayes-an
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The categories of this paper are: eess
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The categories of this paper are: patt-sol
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The categories of this paper are: ao-sci
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The categories of this paper are: comp-gas
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The categories of this paper are: nucl-ex
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The categories of this paper are: stat
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The categories of this paper are: cmp-lg
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The categories of this paper are: atom-ph
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The categories of this paper are: q-alg