Decomposition of the X-ray waveform of soft gamma-ray repeaters during giant flares

We have analyzed the observations of SGR 1806-20 and SGR 1900+14 during giant flares made with the Rossi X-ray Timing Explorer. We have studied the pulsating tail after the initial spike and decomposed the pulse waveform into separate components of sub-pulses. We found evidence for phase shifts of those sub-pulses. This is probably due to rapid geometrical changes in the magnetic field of the neutron star during giant flares. The phase shifts could be used to constrain the geometry of the magnetic field.