Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: UBVRI Photometric Standard Stars Around the Sky at -50 Degrees
  Declination   UBVRI photoelectric observations have been made of 109 stars around the sky,
centered more or less at -50 degrees declination. The majority of the stars
fall in the magnitude range 10.4 < V < 15.5 and in the color index range -0.33
< (B - V) < +1.66. These new broadband photometric standard stars average 16.4
measurements each from data taken on 116 different nights over a period of 4
yr. Similar data are tabulated for 19 stars of interest that were not observed
often enough to make them well-defined standard stars.

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The categories of this paper are: adap-org
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The categories of this paper are: supr-con
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The categories of this paper are: eess
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The categories of this paper are: q-alg
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The categories of this paper are: quant-ph
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The categories of this paper are: plasm-ph
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The categories of this paper are: hep-lat
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The categories of this paper are: mtrl-th
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The categories of this paper are: bayes-an
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The categories of this paper are: nucl-th
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The categories of this paper are: acc-phys
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The categories of this paper are: ao-sci
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The categories of this paper are: cmp-lg
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The categories of this paper are: patt-sol
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The categories of this paper are: nucl-ex
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The categories of this paper are: econ