Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The changing rotational light-curve amplitude of Varuna and evidence for
  a close-in satellite   From CCD observations carried out with different telescopes, we present
short-term photometric measurements of the large trans-Neptunian object Varuna
in 10 epochs, spanning around 19 years. We observe that the amplitude of the
rotational light-curve has changed considerably during this period of time from
0.41 to 0.55 mag. In order to explain this variation, we constructed a model in
which Varuna has a simple triaxial shape, assuming that the main effect comes
from the change of the aspect angle as seen from Earth, due to Varuna's orbital
motion in the 19-year time span. The best fits to the data correspond to a
family of solutions with axial ratios b/a between 0.56 and 0.60. This
constrains the pole orientation in two different ranges of solutions presented
here as maps. Apart from the remarkable variation of the amplitude, we have
detected changes in the overall shape of the rotational light-curve over
shorter time scales. After the analysis of the periodogram of the residuals to
a 6.343572 h double-peaked rotational light-curve fit, we find a clear
additional periodicity. We propose that these changes in the rotational
light-curve shape are due to a large and close-in satellite whose rotation
induces the additional periodicity. The peak-to-valley amplitude of this
oscillation is in the order of 0.04 mag. We estimate that the satellite orbits
Varuna with a period of 11.9819 h (or 23.9638 h), assuming that the satellite
is tidally locked, at a distance of ~ 1300 km (or ~ 2000 km) from Varuna,
outside the Roche limit.

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The categories of this paper are: cmp-lg
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The categories of this paper are: hep-ex
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The categories of this paper are: solv-int
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The categories of this paper are: nucl-th
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The categories of this paper are: atom-ph
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The categories of this paper are: bayes-an
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The categories of this paper are: ao-sci
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The categories of this paper are: physics
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The categories of this paper are: hep-ph
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The categories of this paper are: hep-th
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The categories of this paper are: nucl-ex
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The categories of this paper are: q-fin
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The categories of this paper are: mtrl-th
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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: hep-lat