Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Physical Properties and Evolutionary States of EA-type Eclipsing
  Binaries Observed by LAMOST   About 3196 EA-type binaries (EAs) were observed by LAMOST by June 16, 2017
and their spectral types were derived. Meanwhile stellar atmospheric parameters
of 2020 EAs were determined. In the paper, those EAs are catalogued and their
physical properties and evolutionary states are investigated. The period
distribution of EAs suggests that the period limit of tidal locking for the
close binaries is about 6 days. It is found that the metallicity of EAs is
higher than that of EWs indicating that EAs are generally younger than EWs and
they are the progenitors of EWs. The metallicities of long-period EWs (0.4 < P
< 1 days) are the same as those of EAs with the same periods, while their
values of Log (g) are usually smaller than those of EAs. These support the
evolutionary process that EAs evolve into long-period EWs through the
combination of angular momentum loss (AML) via magnetic braking and case A mass
transfer. For short-period EWs, their metallicities are lower than those of
EAs, while their gravitational accelerations are higher. These reveal that they
may be formed from cool short-period EAs through AML via magnetic braking with
little mass transfer. For some EWs with high metallicities, they may be
contaminated by material from the evolution of unseen neutron stars and black
holes or they have third bodies that may help them to form rapidly through a
short timescale of pre-contact evolution. The present investigation suggests
that the modern EW populations may be formed through the combination of
aforementioned mechanisms.

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The categories of this paper are: chem-ph
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The categories of this paper are: comp-gas
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The categories of this paper are: plasm-ph
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The categories of this paper are: q-alg
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The categories of this paper are: stat
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The categories of this paper are: mtrl-th
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The categories of this paper are: supr-con
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The categories of this paper are: math
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The categories of this paper are: nucl-th
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The categories of this paper are: bayes-an
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The categories of this paper are: nucl-ex
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The categories of this paper are: patt-sol
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The categories of this paper are: q-fin
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The categories of this paper are: hep-th
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The categories of this paper are: dg-ga
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The categories of this paper are: nlin