Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Timing of the young pulsar J1907+0918   We have extensively searched for periodic signals in the area of the soft
gamma-ray repeater SGR 1900+14, at 430 and 1410 MHz with the Arecibo telescope.
Our observations did not reveal the 5.16-s periodicity reported for the
magnetar down to a 430-MHz flux density limit of 150 uJy. During the search we
discovered a 226-ms radio pulsar, PSR J1907+0918. The period derivative implies
the characteristic age for this pulsar is only 38 kyr. Independent evidence in
support of this apparent youth are the unusually high degree of circular
polarization and its relatively flat radio spectrum. The close proximity of PSR
J1907+0918 to SGR 1900+14 suggests that they may have evolved from a massive
binary system. Regardless of this possibility, it is presently not clear to us
that SGR 1900+14 is associated with the supernova remnant G42.8+0.6.

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The categories of this paper are: nlin
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The categories of this paper are: cond-mat
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The categories of this paper are: cmp-lg
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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: comp-gas
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The categories of this paper are: solv-int
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The categories of this paper are: hep-ph
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The categories of this paper are: atom-ph
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The categories of this paper are: physics
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The categories of this paper are: chem-ph
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The categories of this paper are: econ
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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: nucl-th
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The categories of this paper are: patt-sol