A Comprehensive Study of GBM Bursts of SGR J1550-5418

Author: Andrew Collazzi, on behalf of the GBM Magnetar Team

Abstract: Starting in October of 2008 and continuing through April of 2009, the Fermi Gamma-ray Burst Monitor (GBM) observed three periods of activity from SGR J1550-5418. Over the course of these outburst periods, GBM observed several hundred bursts from this source. We have performed analysis on all the bursts, and identified significant spectral evolution between the first and the other two periods. While a single blackbody function best describes the bursts of the first period, a two black body model best describes those of the second; more than one model fits the bursts of the third period equally well (OTTB, BB+BB, Comptonized model). These results show an evolution in the burst emission mechanism of the source. We have analyzed a sample of ∼66 bursts within the tail of the second period to identify the onset of spectral changes, without success. Finally, we present a comprehensive review of all temporal and time-integrated spectral analyses of the entire set of GBM bursts (∼384 bursts) from this source.