Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The masses, radii and luminosities of the components of U Geminorum   We present a phase-resolved spectroscopic study of the secondary star in the
cataclysmic variable U Gem. We use our data to measure the radial velocity
semi-amplitude, systemic velocity and rotational velocity of the secondary
star. Combining this with literature data allows us to determine masses and
radii for both the secondary star and white dwarf which are independent of any
assumptions about their structure. We use these to compare their properties
with those of field stars and find that both components follow field
mass-radius relationships. The secondary star has the mass, radius, luminosity
and photometric temperature of an M2 star, but a spectroscopic temperature of
M4. The latter may well be due to a high metallicity. There is a troubling
inconsistency between the radius of the white dwarf inferred from its
gravitational redshift and inclination and that inferred from its temperature,
flux, and astrometric distance.
  We find that there are two fundamental limits to the accuracy of the
parameters we can derive. First the radial velocity curve of the secondary star
deviates from a sinusoid, in part because of its asphericity (which can be
modelled) and in part because the line flux is not evenly distributed over its
surface. Second we cannot be certain which spectral type is the best match for
the lines of the secondary star, and the derived rotational velocity is a
function of the spectral type of the template star used.

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The categories of this paper are: cs
14
The categories of this paper are: math-ph
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The categories of this paper are: nucl-ex
26
The categories of this paper are: bayes-an
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The categories of this paper are: physics
9
The categories of this paper are: nlin
21
The categories of this paper are: adap-org
25
The categories of this paper are: patt-sol
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The categories of this paper are: dg-ga
35
The categories of this paper are: mtrl-th
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The categories of this paper are: acc-phys
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The categories of this paper are: hep-ph
32
The categories of this paper are: atom-ph
34
The categories of this paper are: chem-ph
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The categories of this paper are: stat
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The categories of this paper are: eess