Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Post-Burst Awakening of the Anomalous X-ray Pulsar in Westerlund 1   On September 21, 2006, an intense (~10^39 erg/s) and short (20 ms) burst was
detected by Swift BAT at a position consistent with that of the candidate
Anomalous X-ray Pulsar, CXOU J164710.2-455216, discovered by Chandra in 2005.
Swift follow-up observations began about 13 hours after the event and found the
source at a 1-10keV flux level of about 4.5 x 10^-11 erg/s/cm^2, i.e. ~300
times brighter than measured 5 days earlier by XMM. We report the results
obtained from Swift BAT observations of the burst and subsequent Swift XRT
observations carried out during the first four months after the burst. These
data are complemented with those from two XMM observations (carried out just
before and after the BAT event) and four archival Chandra observations carried
out between 2005 and 2007. We find a phase coherent solution for the source
pulsations after the burst. The evolution of the pulse phase comprises an
exponential component decaying with timescale of 1.4d which we interpret as the
recovery stage following a large glitch (Delta nu / nu about 6 x 10^-5). We
also detect a quadratic component corresponding to a spin-down rate of Pdot ~ 9
x 10^-13, implying a magnetic field strength of 10^14 Gauss.
  During the first Swift XRT observation taken 0.6 days after the burst, the
spectrum showed a kT = 0.65keV blackbody (R_BB = 1.5km) plus a Gamma=2.3
power-law accounting for about 60% of the 1-10 keV observed flux. Analysis of
Chandra archival data, taken during 2005 when the source was in quiescence,
reveal that the modulation in quiescence is 100% pulsed at energies above 4 keV
and consistent with the (unusually small-sized) blackbody component being
occulted by the neutron star as it rotates.

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The categories of this paper are: gr-qc
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The categories of this paper are: adap-org
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The categories of this paper are: supr-con
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The categories of this paper are: hep-lat
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The categories of this paper are: econ
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The categories of this paper are: hep-ph
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The categories of this paper are: bayes-an
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The categories of this paper are: chem-ph
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The categories of this paper are: q-bio
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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: cs
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The categories of this paper are: math-ph
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The categories of this paper are: cond-mat
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The categories of this paper are: patt-sol