Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Massive Star Population in M101. III. Spectra and Photometry of the
  Luminous and Variable Stars   We discuss moderate resolution spectra, multicolor photometry, and light
curves of thirty-one of the most luminous stars and variables in the giant
spiral M101. The majority are intermediate A to F-type supergiants. We present
new photometry and light curves for three known "irregular blue variables" V2,
V4 and V9) and identify a new candidate. Their spectra and variability confirm
that they are LBV candidates and V9 may be in an LBV-like maximum light state
or eruption.

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The categories of this paper are: math-ph
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The categories of this paper are: funct-an
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The categories of this paper are: physics
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: adap-org
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The categories of this paper are: cmp-lg
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The categories of this paper are: cond-mat
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The categories of this paper are: hep-lat
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The categories of this paper are: dg-ga
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The categories of this paper are: eess
2
The categories of this paper are: math
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The categories of this paper are: q-bio
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The categories of this paper are: nucl-th
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The categories of this paper are: econ
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The categories of this paper are: quant-ph