Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The white dwarf cooling sequence of NGC 6791: a unique tool for stellar
  evolution   NGC 6791 is a well-studied, metal-rich open cluster that is so close to us
that can be imaged down to luminosities fainter than that of the termination of
its white dwarf cooling sequence, thus allowing for an in-depth study of its
white dwarf population. We use a Monte Carlo simulator that employs up-to-date
evolutionary cooling sequences for white dwarfs with hydrogen-rich and
hydrogen-deficient atmospheres, with carbon-oxygen and helium cores. The
cooling sequences for carbon-oxygen cores account for the delays introduced by
both Ne^22 sedimentation in the liquid phase and by carbon-oxygen phase
separation upon crystallization. We do not find evidence for a substantial
fraction of helium-core white dwarfs, and hence our results support the
suggestion that the origin of the bright peak of the white dwarf luminosity
function can only be attributed to a population of unresolved binary white
dwarfs. Moreover, our results indicate that the number distribution of
secondary masses of the population of unresolved binaries has to increase with
increasing mass ratio between the secondary and primary components of the
progenitor system. We also find that the observed cooling sequence appears to
be able to constrain the presence of progenitor sub-populations with different
chemical compositions and the fraction of non-DA white dwarfs. Our simulations
place interesting constraints on important characteristics of the stellar
populations of NGC 6791. In particular, we find that the fraction of single
helium-core white dwarfs must be smaller than 5%, that a sub-population of
stars with zero metallicity must be <12%, while if the adopted metallicity of
the sub-population is solar the upper limit is ~8%. Finally, we also find that
the fraction of non-DA white dwarfs in this particular cluster is surprinsingly
small <6%.

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The categories of this paper are: chao-dyn
14
The categories of this paper are: math-ph
5
The categories of this paper are: gr-qc
26
The categories of this paper are: bayes-an
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The categories of this paper are: hep-th
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The categories of this paper are: q-fin
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The categories of this paper are: quant-ph
11
The categories of this paper are: hep-lat
15
The categories of this paper are: nucl-ex
12
The categories of this paper are: nucl-th
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The categories of this paper are: funct-an
4
The categories of this paper are: cond-mat
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The categories of this paper are: mtrl-th
1
The categories of this paper are: cs
2
The categories of this paper are: math
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The categories of this paper are: solv-int