Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Chandra grating spectroscopy of three hot white dwarfs   High-resolution soft X-ray spectroscopic observations of single hot white
dwarfs are scarce. With the Chandra Low-Energy Transmission Grating, we have
observed two white dwarfs, one is of spectral type DA (LB 1919) and the other
is a non-DA of spectral type PG1159 (PG 1520+525). The spectra of both stars
are analyzed, together with an archival Chandra spectrum of another DA white
dwarf (GD 246). The soft X-ray spectra of the two DA white dwarfs are
investigated in order to study the effect of gravitational settling and
radiative levitation of metals in their photospheres. LB 1919 is of interest
because it has a significantly lower metallicity than DAs with otherwise
similar atmospheric parameters. GD 246 is the only white dwarf known that shows
identifiable individual iron lines in the soft X-ray range. For the PG1159
star, a precise effective temperature determination is performed in order to
confine the position of the blue edge of the GW Vir instability region in the
HRD. (abridged)

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The categories of this paper are: plasm-ph
4
The categories of this paper are: cond-mat
27
The categories of this paper are: comp-gas
23
The categories of this paper are: solv-int
2
The categories of this paper are: math
14
The categories of this paper are: math-ph
8
The categories of this paper are: hep-ex
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The categories of this paper are: q-fin
3
The categories of this paper are: physics
16
The categories of this paper are: stat
1
The categories of this paper are: cs
12
The categories of this paper are: nucl-th
7
The categories of this paper are: hep-th
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The categories of this paper are: patt-sol
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The categories of this paper are: cmp-lg
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The categories of this paper are: q-alg