Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: An investigation of the close environment of beta Cep with the
  VEGA/CHARA interferometer   High-precision interferometric measurements of pulsating stars help to
characterize their close environment. In 1974, a close companion was discovered
around the pulsating star beta Cep using the speckle interferometry technique
and features at the limit of resolution (20 milli-arcsecond or mas) of the
instrument were mentioned that may be due to circumstellar material. Beta Cep
has a magnetic field that might be responsible for a spherical shell or
ring-like structure around the star as described by the MHD models. Using the
visible recombiner VEGA installed on the CHARA long-baseline interferometer at
Mt. Wilson, we aim to determine the angular diameter of beta Cep and resolve
its close environment with a spatial resolution up to 1 mas level. Medium
spectral resolution (R=6000) observations of beta Cep were secured with the
VEGA instrument over the years 2008 and 2009. These observations were performed
with the S1S2 (30m) and W1W2 (100m) baselines of the array. We investigated
several models to reproduce our observations. A large-scale structure of a few
mas is clearly detected around the star with a typical flux relative
contribution of 0.23 +- 0.02. Our best model is a co-rotational geometrical
thin ring around the star as predicted by magnetically-confined wind shock
models. The ring inner diameter is 8.2 +- 0.8 mas and the width is 0.6 +- 0.7
mas. The orientation of the rotation axis on the plane of the sky is PA = 60 +-
1 deg, while the best fit of the mean angular diameter of beta Cep gives UD[V]
= 0.22 +- 0.05 mas. Our data are compatible with the predicted position of the
close companion of beta Cep. These results bring additional constraints on the
fundamental parameters and on the future MHD and asteroseismological models of
the star.

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The categories of this paper are: quant-ph
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The categories of this paper are: q-fin
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The categories of this paper are: math-ph
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The categories of this paper are: chem-ph
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The categories of this paper are: cond-mat
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The categories of this paper are: plasm-ph
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The categories of this paper are: q-bio
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The categories of this paper are: acc-phys
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The categories of this paper are: q-alg
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The categories of this paper are: patt-sol
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The categories of this paper are: atom-ph
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The categories of this paper are: hep-ex
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The categories of this paper are: alg-geom
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The categories of this paper are: bayes-an
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The categories of this paper are: chao-dyn
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The categories of this paper are: eess