Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Consequences of Hipparcos parallaxes for stellar evolutionary models.
  Three Hyades binaries: V818 Tauri, 51 Tauri, and $\theta^2$ Tauri   Three binary systems in the Hyades open cluster (51 Tau, V818 Tau, and
$\theta^2$ Tau}, with known metallicity and good Johnson photometric data are
used to test the validity of three independent sets of stellar evolutionary
tracks. A statistical method is described and applied to the colour-magnitude
diagram of the six selected components, giving rise to $\chi^2$-contours in the
metallicity--age plane. The effects of the Hipparcos parallaxes on these
confidence regions are studied in detail for these binaries through a
comparison with very accurate but older orbital parallaxes. There are no
significant differences in 51 Tau and $\theta^2$ Tau, and hence the test
validates the sets of theoretical tracks used. However the orbital parallax of
V818 Tau leads to metallicities too large in comparison with the observed
range, while the Hipparcos parallax give consistent results, at the 1$\sigma$
level. Comparisons between the predicted and measured masses are also made and
show a good agreement. However, even if the Padova tracks predict correct
masses for each component of V818 Tau, there is no Padova track that fits both
components simultaneously in the mass-radius diagram. Finally, since the
individual masses of these binaries are accurately known, some issues about the
influence of the Hipparcos parallaxes on their location in the mass-luminosity
diagram are also discussed.

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The categories of this paper are: patt-sol
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The categories of this paper are: plasm-ph
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The categories of this paper are: nlin
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The categories of this paper are: hep-th
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The categories of this paper are: physics
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The categories of this paper are: cmp-lg
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The categories of this paper are: atom-ph
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The categories of this paper are: comp-gas
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The categories of this paper are: funct-an
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The categories of this paper are: cond-mat
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The categories of this paper are: eess
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The categories of this paper are: alg-geom
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The categories of this paper are: solv-int
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The categories of this paper are: nucl-ex
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The categories of this paper are: chao-dyn
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The categories of this paper are: q-fin