Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On the X-ray Spectra of Anomalous X-ray Pulsars and Soft Gamma Repeaters   We revisit the apparent correlation between soft X-ray band photon index and
spin-down rate nudot previously reported for Anomalous X-ray Pulsars (AXPs) and
Soft Gamma Repeaters (SGRs) by Marsden & White (2001). Our analysis, improved
thanks to new source discoveries, better spectral parameter measurements in
previously known sources, and the requirement of source quiescence for
parameter inclusion, shows evidence for the previously noted trend, although
with greater scatter. This trend supports the twisted magnetosphere model of
magnetars although the scatter suggests that factors other than nudot are also
important. We also note possible correlations involving the spectra of AXPs and
SGRs in the hard X-ray band. Specifically, the hard-band photon index shows a
possible correlation with inferred nudot and B, as does the degree of spectral
turnover. If the former trend is correct, then the hard-band photon index for
AXP 1E 1048.1-5937 should be ~0--1. This may be testable with long integrations
by INTEGRAL, or by the upcoming focussing hard X-ray mission NuSTAR.

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The categories of this paper are: funct-an
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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: stat
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The categories of this paper are: physics
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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: nucl-th
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The categories of this paper are: hep-lat
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The categories of this paper are: adap-org
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The categories of this paper are: bayes-an
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The categories of this paper are: hep-th
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The categories of this paper are: acc-phys
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The categories of this paper are: econ
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The categories of this paper are: math
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The categories of this paper are: eess