Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Discovery of a Neutron Star with a Spin Frequency of 530 Hz in
  A1744-361   We report the detection with the Rossi X-ray Timing Explorer (RXTE)
Proportional Counter Array (PCA) of 530 Hz burst oscillations in a
thermonuclear (type I) burst from the transient X-ray source A1744-361. This is
only the second burst ever observed from this source, and the first to be seen
in any detail. Our results confirm that A1744-361 is a low mass X-ray binary
(LMXB) system harboring a rapidly rotating neutron star. The oscillations are
first detected along the rising edge of the burst, and they show evidence for
frequency evolution of a magnitude similar to that seen in other burst sources.
The modulation amplitude and its increase with photon energy are also typical
of burst oscillations. The lack of any strong indication of photospheric radius
expansion during the burst suggests a 9 kpc upper limit of the source distance.
We also find energy dependent dips, establishing A1744-361 as a high
inclination, dipping LMXB. The timescale between the two episodes of observed
dips suggests an orbital period of ~ 97 minutes. We have also detected a 2 - 4
Hz quasi-periodic-oscillation (QPO) for the first time from this source. This
QPO appears consistent with ~ 1 Hz QPOs seen from other high-inclination
systems. We searched for kilohertz QPOs, and found a suggestive 2.3 sigma
feature at 800 Hz in one observation. The frequency, strength, and quality
factor are consistent with that of a lower frequency kilohertz QPO, but the
relatively low significance argues for caution, so we consider this a tentative
detection requiring confirmation.

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The categories of this paper are: econ
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The categories of this paper are: solv-int
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The categories of this paper are: atom-ph
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The categories of this paper are: mtrl-th
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The categories of this paper are: hep-th
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The categories of this paper are: math
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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: nucl-th
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The categories of this paper are: q-alg
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The categories of this paper are: eess
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The categories of this paper are: chao-dyn
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The categories of this paper are: patt-sol
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The categories of this paper are: stat
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The categories of this paper are: q-bio
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The categories of this paper are: alg-geom