Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A study of the long term variability of RX J1856.5-3754 with XMM-Newton   We report on a detailed spectral analysis of all the available XMM-Newton
data of RX J1856.5-3754, the brightest and most extensively observed nearby,
thermally emitting neutron star. Very small variations (~1-2%) in the
single-blackbody temperature are detected, but are probably due to an
instrumental effect, since they correlate with the position of the source on
the detector. Restricting the analysis to a homogeneous subset of observations,
with the source at the same detector position, we place strong limits on
possible spectral or flux variations from March 2005 to present-day. A slightly
higher temperature (kT~61.5 eV, compared to the average value kT~61 eV) was
instead measured in April 2002. If this difference is not of instrumental
origin, it implies a rate of variation of about 0.15 eV/yr between April 2002
and March 2005. The high-statistics spectrum from the selected observations is
well fit by the sum of two blackbody models, which extrapolate to an optical
flux level in agreement with the observed value.

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The categories of this paper are: funct-an
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The categories of this paper are: gr-qc
1
The categories of this paper are: cs
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The categories of this paper are: plasm-ph
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The categories of this paper are: comp-gas
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The categories of this paper are: stat
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The categories of this paper are: acc-phys
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The categories of this paper are: q-fin
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The categories of this paper are: dg-ga
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The categories of this paper are: econ
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The categories of this paper are: ao-sci
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The categories of this paper are: math-ph
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The categories of this paper are: alg-geom
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The categories of this paper are: physics
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The categories of this paper are: math
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The categories of this paper are: q-alg