Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The ultraluminous X-ray sources NGC 1313 X-1 and X-2: a broadband study
  with NuSTAR and XMM-Newton   We present the results of NuSTAR and XMM-Newton observations of the two
ultraluminous X-ray sources (ULX) NGC 1313 X-1 and X-2. The combined spectral
bandpass of the two satellites enables us to produce the first spectrum of X-1
between 0.3 and 30 keV, while X-2 is not significantly detected by NuSTAR above
10 keV. The NuSTAR data demonstrate that X-1 has a clear cutoff above 10 keV,
whose presence was only marginally detectable with previous X-ray observations.
This cutoff rules out the interpretation of X-1 as a black hole in a standard
low/hard state, and it is deeper than predicted for the downturn of a broadened
iron line in a reflection-dominated regime. The cutoff differs from the
prediction of a single-temperature Comptonization model. Further, a cold
disk-like black body component at ~0.3 keV is required by the data, confirming
previous measurements by XMM-Newton only. We observe a spectral transition in
X-2, from a state with high luminosity and strong variability to a
lower-luminosity state with no detectable variability, and we link this
behavior to a transition from a super-Eddington to a sub-Eddington regime.

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The categories of this paper are: cs
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The categories of this paper are: patt-sol
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The categories of this paper are: acc-phys
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The categories of this paper are: nucl-ex
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The categories of this paper are: cond-mat
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The categories of this paper are: eess
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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: mtrl-th
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The categories of this paper are: hep-lat
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The categories of this paper are: hep-ph
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The categories of this paper are: funct-an
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The categories of this paper are: hep-ex
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The categories of this paper are: gr-qc
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The categories of this paper are: hep-th
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The categories of this paper are: math