Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: PSR J1024-0719: A Millisecond Pulsar in an Unusual Long-Period Orbit   PSR J1024$-$0719 is a millisecond pulsar that was long thought to be
isolated. However, puzzling results concerning its velocity, distance, and low
rotational period derivative have led to reexamination of its properties. We
present updated radio timing observations along with new and archival optical
data that show PSR J1024$-$0719 is most likely in a long period (2$-$20 kyr)
binary system with a low-mass ($\approx 0.4\,M_\odot$) low-metallicity ($Z
\approx -0.9\,$ dex) main sequence star. Such a system can explain most of the
anomalous properties of this pulsar. We suggest that this system formed through
a dynamical exchange in a globular cluster that ejected it into a halo orbit,
consistent with the low observed metallicity for the stellar companion. Further
astrometric and radio timing observations such as measurement of the third
period derivative could strongly constrain the range of orbital parameters.

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The categories of this paper are: solv-int
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The categories of this paper are: cs
18
The categories of this paper are: econ
21
The categories of this paper are: adap-org
8
The categories of this paper are: hep-ex
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The categories of this paper are: nucl-th
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The categories of this paper are: acc-phys
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The categories of this paper are: supr-con
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The categories of this paper are: q-fin
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The categories of this paper are: stat
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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: patt-sol
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The categories of this paper are: dg-ga
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The categories of this paper are: plasm-ph
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The categories of this paper are: cmp-lg