  We describe XMM-Newton observations taken 4.3 days prior to and 1.5 days
subsequent to two remarkable events that were detected with Swift on 2006
September 21 from the candidate magnetar CXOU J164710.2-455216: (1) a 20 ms
burst with an energy of 1e37 erg (15-150 keV), and (2) a rapid spin-down
(glitch) with a fractionap period change of 1e-4. We find that the luminosity
of the pulsar increased by a factor of 100 in the interval between
observations, from 1e33 to 1e35 erg/s (0.5-8.0 keV), and that its spectrum
hardened. The pulsed count rate increased by a factor of 10 (0.5-8.0 keV), but
the fractional rms amplitude of the pulses decreased from 65 to 11 per cent,
and their profile changed from being single-peaked to exhibiting three peaks.
Similar changes have been observed from other magnetars in response to
outbursts, such as that of 1E 2259+586 in 2002 June. We suggest that a plastic
deformation of the neutron star's crust induced a very slight twist in the
external magnetic field, which in turn generated currents in the magnetosphere
that were the direct cause of the X-ray outburst.
