Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: What can we learn from the surface chemical composition of the optical
  companions of Soft X-ray transients?   Several evolutionary sequences with low--mass secondaries ($M_d $=1.25, 1.5
and 1.7$ M_\odot $) and black hole accretors ($M_{bh} $=5 and 10$ M_\odot$) are
calculated. The angular momentum losses due to magnetic braking and
gravitational wave radiation are included. Using full nuclear networks (p--p
and CNO cycles) we follow carefully the evolution of the surface composition of
the secondary star. We find that the surface chemical composition of the
secondary star may give additional information which helps to understand the
formation of soft X-ray transients with black holes as accretors. We show that
observations of isotope ratios $^{12}C/^{13}C$, $^{14}N/^{15}N$ and
$^{16}O/^{17}O $ with comparison to computed sequences allow estimates
independent from spectroscopy of the mass of the secondary component. We find
that our evolutionary calculations satisfactorily explain the observed $\it q =
M_{sg}/M_{bh}$ -- $P_{orb}$ distribution for Soft X-ray transients with orbital
periods less than one day. Using our evolutionary calculations we estimate
secondary masses and surface chemical abundances (C,N,O) for different systems.
We distinguished three different phases in the SXT's evolution. The optical
component shows (i) cosmic C, N, O abundances and $^{12}$C/$^{13}$C isotopic
ratio; (ii) cosmic C, N, O abundances but modified $^{12}$C/$^{13}$C ratio; and
(iii) depletion of C and enhanced of N abundances and strongly modified
isotopic ratios of C, N, O elements.

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The categories of this paper are: cmp-lg
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The categories of this paper are: chao-dyn
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The categories of this paper are: mtrl-th
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The categories of this paper are: chem-ph
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The categories of this paper are: econ
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The categories of this paper are: dg-ga
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The categories of this paper are: nucl-th
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The categories of this paper are: hep-th
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The categories of this paper are: acc-phys
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The categories of this paper are: cond-mat
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The categories of this paper are: adap-org
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The categories of this paper are: patt-sol
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The categories of this paper are: funct-an
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The categories of this paper are: hep-ex
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The categories of this paper are: nlin
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The categories of this paper are: alg-geom