The 2009 Fermi Symposium

Fermi-GBM Detection of Hard X-ray Pulsations in the Persistent X-ray Emission of SGR 1550-5418/AXP 1E 1547.0-5408

Ersin Gogus

Abstract:

SGR 1550-5418 (previously known as AXP 1E 1547.0-5408) displayed three active bursting episodes in Oct 2008, Jan-Feb 2009, and Mar-Apr 2009, emitting hundreds of typical soft gamma-ray bursts. We have iden.fied a ~120-s-long data segment during one of the episodes that exhibited intriguing spectral and .ming properties: persistent emission clearly above the background level including short bursts aligned with the maxima of the spin phase of the neutron star. By analyzing all available data of this enhanced emission, we discovered: (i) the spectrum of the enhanced emission alone (after removing the bursts) requires an additional component, possibly a blackbody with kt~16 keV; (ii) the pulsations at the spin frequency of the neutron star are clearly detected up to ~ 130 keV; (iii) the pulsed fraction is energy dependent and at its highest level (65%) in the 50-74 keV band. Here, we present our results and discuss possible interpretations.