Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: K I 7699 {\AA} and related shell lines during the recent eclipse of
  $\epsilon$ Aurigae   We report high-resolution (R = 30\ 000, 45\ 000 and 75\ 000) echelle and
medium-resolution (R = 22\ 000 and 10\ 000) spectroscopic observations of the
long-period, eclipsing binary $\epsilon$ Aurigae during the 2009 - 2011
eclipse. Low-excitation shell lines, viz, the K {\sevensize \rm I} line at 7699
\AA\ (with 346 data points), Cr {\sevensize \rm I} lines at 5345.807 \AA\ and
5348.326 \AA\ and Fe {\sevensize \rm I} line at 5110.435 \AA\ which originated
from the disk shaped secondary, H$\alpha$ and the shell components of the Na
D$_{1}$ and D$_{2}$ lines show significant variation in their shapes and radial
velocities during the eclipse. The equivalent width curve shown by the K
{\sevensize \rm I} line around the ingress and egress phases indicates that the
gas density in the trailing edge is about a factor of two higher than the
density in the leading edge. Using a geometrical model, in which a homogeneous,
cylindrical Keplarian disk eclipses the F0Ia primary star and the shell
absorption lines originate from the gaseous atmosphere around an opaque disk,
we fit the equivalent width and the radial velocity curves of the K {\sevensize
\rm I} line covering the full eclipse. A reasonably good fit can be achieved by
a low-mass binary model where the mass of the central star of the disk is 5.4
M$_{\odot}$ and the mass of the primary is 2.5 M$_{\odot}$ and a disk size of
8.9 AU. The low-mass of the primary, with enhanced $s$-process elements found
by Sadakane et al. (2010), supports that it is a post-AGB F supergiant. For the
high-mass binary model, the modelled radial velocity curve deviates
significantly from the observations.

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The categories of this paper are: comp-gas
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The categories of this paper are: alg-geom
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The categories of this paper are: nlin
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The categories of this paper are: physics
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The categories of this paper are: q-alg
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The categories of this paper are: ao-sci
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The categories of this paper are: atom-ph
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The categories of this paper are: q-fin
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The categories of this paper are: plasm-ph
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The categories of this paper are: hep-ph
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The categories of this paper are: bayes-an
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The categories of this paper are: dg-ga
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The categories of this paper are: eess
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The categories of this paper are: hep-lat
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The categories of this paper are: econ
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The categories of this paper are: funct-an