Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Opacity modelling of heavy-metal hot subdwarfs. Photoionization of
  Sr$^0$, Y$^{+}$ and Zr$^{2+}$   Heavy-metal hot subdwarfs (sdB and sdO) represent a small group of stars with
unusually high concentrations of trans-iron elements in their atmospheres,
having abundances ~ 10000 times solar. One example is LS IV-14$^{\circ}$ 116,
where a number of heavy-metal absorption lines of Sr II, Y III and Zr IV have
been observed in the optical band 4000 - 5000 A. We use a fully relativistic
Dirac atomic R-Matrix (DARC) to calculate photoionization cross sections of
Sr$^{0}$, Y$^{+}$ and Zr$^{2+}$ from their ground state to the twentieth
excited level. We use the cross sections and the oscillator strengths to
simulate the spectrum of a hot subdwarf. We obtain complete sets of
photoionization cross sections for the three ions under study. We use these
data to calculate the opacity of the stellar atmospheres of hot subdwarf stars,
and show that for overabundances observed in some heavy-metal subdwarves,
photo-excitation from zirconium, in particular, does contribute some back
warming in the model.

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The categories of this paper are: chao-dyn
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The categories of this paper are: dg-ga
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The categories of this paper are: nucl-ex
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The categories of this paper are: quant-ph
30
The categories of this paper are: q-alg
5
The categories of this paper are: gr-qc
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The categories of this paper are: adap-org
36
The categories of this paper are: cmp-lg
1
The categories of this paper are: cs
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The categories of this paper are: q-fin
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The categories of this paper are: econ
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The categories of this paper are: alg-geom
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The categories of this paper are: chem-ph
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The categories of this paper are: comp-gas
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The categories of this paper are: plasm-ph
0
The categories of this paper are: hep-ph