Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Early-type stars in the young open cluster NGC 2244 and in the Mon OB2
  association I. The multiplicity of O-type stars   Aims. We present the results obtained from a long-term spectroscopic campaign
devoted to the multiplicity of O-type stars in the young open cluster NGC2244
and in the Mon OB2 association. Methods. Our spectroscopic monitoring was
performed over several years, allowing us to probe different time-scales. For
each star, several spectral diagnostic tools are applied, in order to search
for line shifts and profile variations. We also measure the projected
rotational velocity and revisit the spectral classification. Results. In our
sample, several stars were previously considered as spectroscopic binaries,
though only a few scattered observations were available. Our results now reveal
a more complex situation. Our study identifies two new spectroscopic binaries
(HD46149 in NGC2244 and HD46573 in MonOB2). The first object is a long-period
double-lined spectroscopic binary, though the exact value of its period remains
uncertain and the second object is classified as an SB1 system with a period of
about 10.67 days but the time series of our observations do not enable us to
derive a unique orbital solution for this system. We also classify another star
as variable in radial velocity (HD46150) and we detect line profile variations
in two rapid rotators (HD46056 and HD46485). Conclusions. This spectroscopic
investigation places a firm lower limit (17%) on the binary fraction of O-stars
in NGC2244 and reveals the lack of short-period O+OB systems in this cluster.
In addition, a comparison of these new results with two other well-studied
clusters (NGC6231 and IC1805) puts forward possible hints of a relation between
stellar density and binarity, which could provide constraints on the theories
about the formation and early evolution of hot stars.

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The categories of this paper are: hep-ex
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The categories of this paper are: atom-ph
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The categories of this paper are: hep-lat
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The categories of this paper are: gr-qc
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The categories of this paper are: supr-con
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The categories of this paper are: physics
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The categories of this paper are: nucl-ex
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The categories of this paper are: q-alg
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The categories of this paper are: acc-phys
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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: math-ph
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The categories of this paper are: stat
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The categories of this paper are: q-fin
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The categories of this paper are: cs
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The categories of this paper are: funct-an