Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Magnetar Twists: Fermi/Gamma ray Burst Monitor (GBM) detection of SGR
  J1550-5418   SGR J1550-5418 (previously known as AXP 1E 1547.0-5408 or PSR J1550-5418)
went into three active bursting episodes in 2008 October and in 2009 January
and March, emitting hundreds of typical Soft Gamma Repeater (SGR) bursts in
soft gamma-rays. The second episode was especially intense, and our untriggered
burst search on Fermi/GBM data (8-1000 keV) revealed ~450 bursts emitted over
24 hours during the peak of this activity. Using the GBM data, we identified a
~150-s-long enhanced persistent emission during 2009 January 22 that exhibited
intriguing timing and spectral properties: (i) clear pulsations up to ~110 keV
at the spin period of the neutron star (P ~ 2.07 s, the fastest of all
magnetars), (ii) an additional (to a power-law) blackbody component required
for the enhanced emission spectra with kT ~ 17 keV, (iii) pulsed fraction that
is strongly energy dependent and highest in the 50-74 keV energy band. A total
isotropic-equivalent energy emitted during this enhanced emission is estimated
to be 2.9 x 10^{40} (D/5 kpc)^2 erg. The estimated area of the blackbody
emitting region of ~0.046(D/5 kpc)^2 km^2 (roughly a few x 10^{-5} of the
neutron star area) is the smallest "hot spot" ever measured for a magnetar and
most likely corresponds to the size of magnetically-confined plasma near the
neutron star surface.

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The categories of this paper are: mtrl-th
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The categories of this paper are: physics
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The categories of this paper are: q-bio
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The categories of this paper are: hep-th
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The categories of this paper are: hep-ex
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The categories of this paper are: econ
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The categories of this paper are: quant-ph
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The categories of this paper are: acc-phys
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The categories of this paper are: math-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: solv-int
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The categories of this paper are: funct-an
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The categories of this paper are: alg-geom
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The categories of this paper are: nlin
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The categories of this paper are: chao-dyn
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The categories of this paper are: nucl-ex