Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Mass ratio from Doppler beaming and R{\o}mer delay versus ellipsoidal
  modulation in the Kepler data of KOI-74   We present a light curve analysis and radial velocity study of KOI-74, an
eclipsing A star + white dwarf binary with a 5.2 day orbit. Aside from new
spectroscopy covering the orbit of the system, we used 212 days of publicly
available Kepler observations and present the first complete light curve
fitting to these data, modelling the eclipses and transits, ellipsoidal
modulation, reflection, and Doppler beaming. Markov Chain Monte Carlo
simulations are used to determine the system parameters and uncertainty
estimates. Our results are in agreement with earlier studies, except that we
find an inclination of 87.0 \pm 0.4\degree, which is significantly lower than
the previously published value. We find that the mass ratio derived from the
radial velocity amplitude (q=0.104 \pm 0.004) disagrees with that derived from
the ellipsoidal modulation (q=0.052 \pm 0.004} assuming corotation). This was
found before, but with our smaller inclination, the discrepancy is even larger
than previously reported. Accounting for the rapid rotation of the A-star is
found to increase the discrepancy even further by lowering the mass ratio to
q=0.047 \pm 0.004. These results indicate that one has to be extremely careful
in using the amplitude of an ellipsoidal modulation signal in a close binary to
determine the mass ratio, when a proof of corotation is not firmly established.
The radial velocities that can be inferred from the detected Doppler beaming in
the light curve are found to be in agreement with our spectroscopic radial
velocity determination. We also report the first measurement of R{\o}mer delay
in a light curve of a compact binary. This delay amounts to -56 \pm 17 s and is
consistent with the mass ratio derived from the radial velocity amplitude. The
firm establishment of this mass ratio at q=0.104 \pm 0.004 leaves little doubt
that the companion of KOI-74 is a low mass white dwarf.

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The categories of this paper are: funct-an
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The categories of this paper are: cmp-lg
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The categories of this paper are: cond-mat
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The categories of this paper are: atom-ph
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The categories of this paper are: chem-ph
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The categories of this paper are: cs
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The categories of this paper are: nucl-ex
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The categories of this paper are: hep-lat
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The categories of this paper are: mtrl-th
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The categories of this paper are: stat
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The categories of this paper are: q-fin
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The categories of this paper are: q-bio
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The categories of this paper are: dg-ga
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The categories of this paper are: physics
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The categories of this paper are: quant-ph
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The categories of this paper are: gr-qc