Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Quasi Periodic Oscillations and Strongly Comptonized X-ray emission from
  Holmberg IX X-1   We report the discovery of a 200mHz quasi-periodic oscillation (QPO) in the
X-ray emission from a bright ultra-luminous X-ray source (ULX) Holmberg IX X-1
using a long XMM-Newton observation. The QPO has a centroid at
202.5_{-3.8}^{+4.9}mHz, a coherence Q ~9.3 and an amplitude (rms) of 6% in the
0.2-10keV band. This is only the second detection of a QPO from an ULX, after
M82 X-1, and provides strong evidence against beaming. The power spectrum is
well fitted by a power law with an index of ~0.7. The total integrated power
(rms) is ~9.4% in the 0.001-1Hz range. The X-ray spectrum shows clear evidence
for a soft X-ray excess component that is well described by a multicolor disk
blackbody (kT_in ~ 0.3keV) and a high energy curvature that can be modeled
either by a cut-off power law (Gamma ~ 1; E_cutoff ~9keV) or as a strongly
Comptonized continuum in an optically thick (tau ~7.3) and cool (kT_e ~3keV)
plasma. Both the presence of the QPO and the shape of the X-ray spectrum
strongly suggest that the ULX is not in the high/soft or thermally dominated
state. A truncated disk and inner optically thick corona may explain the
observed X-ray spectrum and the presence of the QPO.

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The categories of this paper are: mtrl-th
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The categories of this paper are: math-ph
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The categories of this paper are: nlin
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The categories of this paper are: quant-ph
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The categories of this paper are: supr-con
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The categories of this paper are: math
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The categories of this paper are: comp-gas
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The categories of this paper are: cs
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The categories of this paper are: hep-th
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The categories of this paper are: patt-sol
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The categories of this paper are: q-alg
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The categories of this paper are: adap-org
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The categories of this paper are: hep-lat
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The categories of this paper are: physics
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The categories of this paper are: solv-int
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The categories of this paper are: econ