Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Catching a planet: A tidal capture origin for the exomoon candidate
  Kepler 1625b I   The (yet-to-be confirmed) discovery of a Neptune-sized moon around the ~3.2
Jupiter-mass planet in Kepler 1625 puts interesting constraints on the
formation of the system. In particular, the relatively wide orbit of the moon
around the planet, at ~40 planetary radii, is hard to reconcile with planet
formation theories. We demonstrate that the observed characteristics of the
system can be explained from the tidal capture of a secondary planet in the
young system. After a quick phase of tidal circularization, the lunar orbit,
initially much tighter than 40 planetary radii, subsequently gradually widened
due to tidal synchronization of the spin of the planet with the orbit,
resulting in a synchronous planet-moon system. Interestingly, in our scenario
the captured object was originally a Neptune-like planet, turned into a moon by
its capture.

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The categories of this paper are: hep-ex
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The categories of this paper are: comp-gas
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The categories of this paper are: math
37
The categories of this paper are: supr-con
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The categories of this paper are: alg-geom
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The categories of this paper are: nucl-ex
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The categories of this paper are: nlin
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The categories of this paper are: ao-sci
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The categories of this paper are: funct-an
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The categories of this paper are: hep-lat
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The categories of this paper are: chao-dyn
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The categories of this paper are: q-fin
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The categories of this paper are: gr-qc
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The categories of this paper are: eess
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The categories of this paper are: hep-ph
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The categories of this paper are: math-ph