Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: XMM-Newton Finds That SAX J1750.8-2900 May Harbor the Hottest, Most
  Luminous Known Neutron Star   We have performed the first sensitive X-ray observation of the low-mass X-ray
binary SAX J1750.8-2900 in quiescence with XMM-Newton. The spectrum was fit to
both a classical black body model, and a non-magnetized, pure hydrogen neutron
star atmosphere model. A power law component was added to these models, but we
found that it was not required by the fits. The distance to SAX J1750.8-2900 is
known to be D = 6.79 kpc from a previous analysis of photospheric radius
expansion bursts. This distance implies a bolometric luminosity (as given by
the NS atmosphere model) of (1.05 +/- 0.12) x 10^34 (D/6.79 kpc)^2 erg s^-1,
which is the highest known luminosity for a NS LMXB in quiescence. One simple
explanation for this surprising result could be that the crust and core of the
NS were not in thermal equilibrium during the observation. We argue that this
was likely not the case, and that the core temperature of the NS in SAX
J1750.8-2900 is unusually high.

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The categories of this paper are: solv-int
33
The categories of this paper are: plasm-ph
12
The categories of this paper are: nucl-th
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The categories of this paper are: adap-org
4
The categories of this paper are: cond-mat
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The categories of this paper are: comp-gas
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The categories of this paper are: funct-an
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The categories of this paper are: math-ph
32
The categories of this paper are: atom-ph
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The categories of this paper are: chao-dyn
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The categories of this paper are: nucl-ex
0
The categories of this paper are: hep-ph
2
The categories of this paper are: math
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The categories of this paper are: dg-ga
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The categories of this paper are: q-fin
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The categories of this paper are: hep-ex