Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: White Dwarf Donors in Ultracompact Binaries: The Stellar Structure of
  Finite Entropy Objects   We discuss the mass-radius (M-R) relations for low-mass (M<0.1 Msun) white
dwarfs (WDs) of arbitrary degeneracy and evolved (He, C, O) composition. We do
so with both a simple analytical model and models calculated by integration of
hydrostatic balance using a modern equation of state valid for fully ionized
plasmas. The M-R plane is divided into three regions where either Coulomb
physics, degenerate electrons or a classical gas dominate the WD structure. For
a given M and central temperature, T_c, the M-R relation has two branches
differentiated by the model's entropy content. We present the M-R relations for
a sequence of constant entropy WDs of arbitrary degeneracy parameterized by M
and T_c for pure He, C, and O. We discuss the applications of these models to
the recently discovered accreting millisecond pulsars. We show the relationship
between the orbital inclination for these binaries and the donor's composition
and T_c. In particular we find from orbital inclination constraints that the
probability XTE J1807-294 can accommodate a He donor is approximately 15% while
for XTE J0929-304, it is approximately 35%. We argue that if the donors in
ultracompact systems evolve adiabatically, there should be 60-160 more systems
at orbital periods of 40 min than at orbital periods of 10 min, depending on
the donor's composition.

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The categories of this paper are: cond-mat
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The categories of this paper are: dg-ga
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The categories of this paper are: funct-an
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The categories of this paper are: atom-ph
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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: cs
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The categories of this paper are: econ
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The categories of this paper are: chem-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: nlin
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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: stat
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The categories of this paper are: alg-geom
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The categories of this paper are: supr-con