Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Discovery of kilohertz quasi-periodic oscillations and state transitions
  in the low-mass X-ray binary 1E~1724-3045 (Terzan 2)   We have studied the rapid X-ray time variability in 99 pointed observations
with the Rossi X-ray Timing Explorer (RXTE)'s Proportional Counter Array of the
low-mass X-ray binary 1E~1724--3045 which includes, for the first time,
observations of this source in its island and banana states, confirming the
atoll nature of this source. We report the discovery of kilohertz
quasi-periodic oscillations (kHz QPOs). Although we have 5 detections of the
lower kHz QPO and one detection of the upper kHz QPO, in none of the
observations we detect both QPOs simultaneously. By comparing the dependence of
the rms amplitude with energy of kHz QPOs in different atoll sources, we
conclude that this information cannot be use to unambiguously identify the
kilohertz QPOs as was previously thought. We find that Terzan~2 in its
different states shows timing behavior similar to that seen in other
neutron-star low mass X-ray binaries (LMXBs). We studied the flux transitions
observed between February 2004 and October 2005 and conclude that they are due
to changes in the accretion rate.

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The categories of this paper are: hep-ex
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The categories of this paper are: funct-an
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The categories of this paper are: adap-org
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The categories of this paper are: chem-ph
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The categories of this paper are: atom-ph
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The categories of this paper are: eess
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The categories of this paper are: nucl-ex
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The categories of this paper are: solv-int
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The categories of this paper are: acc-phys
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The categories of this paper are: mtrl-th
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The categories of this paper are: hep-ph
30
The categories of this paper are: q-alg
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The categories of this paper are: patt-sol
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The categories of this paper are: q-bio
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The categories of this paper are: math
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The categories of this paper are: gr-qc