Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Sub-mm free-free emission from the winds of massive stars in the age of
  ALMA   The thermal radio and sub-mm emission from the winds of massive stars is
investigated and the contribution to the emission due to the stellar wind
acceleration region and clumping of the wind is quantified. Building upon
established theory, a method for calculating the thermal radio and sub-mm
emission using results for a line-driven stellar outflow according to Castor,
Abbott & Klein (1975) is presented. The results show strong variation of the
spectral index for 10 2 GHz < {\nu} < 10 4 GHz. This corresponds both to the
wind acceleration region and clumping of the wind, leading to a strong
dependence on the wind velocity law and clumping parameters. The Atacama Large
Millimeter/sub-mm Array (ALMA) is the first observatory to have both the
spectral window and sensitivity to observe at the high frequencies required to
probe the acceleration regions of massive stars. The deviations in the
predicted flux levels as a result of the inclusion of the wind acceleration
region and clumping are sufficient to be detected by ALMA, through deviations
in the spectral index in different portions of the radio/sub-mm spectra of
massive stars, for a range of reasonable mass-loss rates and distances.
Consequently both mechanisms need to be included to fully understand the
mass-loss rates of massive stars.

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The categories of this paper are: q-alg
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The categories of this paper are: dg-ga
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The categories of this paper are: ao-sci
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The categories of this paper are: nucl-th
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The categories of this paper are: supr-con
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The categories of this paper are: nlin
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The categories of this paper are: cmp-lg
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The categories of this paper are: hep-lat
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The categories of this paper are: eess
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The categories of this paper are: chem-ph
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The categories of this paper are: alg-geom
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The categories of this paper are: acc-phys
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The categories of this paper are: adap-org
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The categories of this paper are: gr-qc
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The categories of this paper are: solv-int
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The categories of this paper are: bayes-an