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We have performed detailed temporal and time-integrated spectral analysis of286 bursts from SGR J1550-5418 detected with the Fermi Gamma-ray Burst Monitor(GBM) in January 2009, resulting in the largest uniform sample of temporal andspectral properties of SGR J1550-5418 bursts. We have used the combination ofbroadband and high time-resolution data provided with GBM to performstatistical studies for the source properties. We determine the durations,emission times, duty cycles and rise times for all bursts, and find that theyare typical of SGR bursts. We explore various models in our spectral analysis,and conclude that the spectra of SGR J1550-5418 bursts in the 8-200 keV bandare equally well described by optically thin thermal bremsstrahlung (OTTB), apower law with an exponential cutoff (Comptonized model), and two black-bodyfunctions (BB+BB). In the spectral fits with the Comptonized model we find amean power-law index of -0.92, close to the OTTB index of -1. We show thatthere is an anti-correlation between the Comptonized Epeak and the burstfluence and average flux. For the BB+BB fits we find that the fluences andemission areas of the two blackbody functions are correlated. Thelow-temperature BB has an emission area comparable to the neutron star surfacearea, independent of the temperature, while the high-temperature blackbody hasa much smaller area and shows an anti-correlation between emission area andtemperature. We compare the properties of these bursts with bursts observedfrom other SGR sources during extreme activations, and discuss the implicationsof our results in the context of magnetar burst models.

SGR J1550-5418 bursts detected with the Fermi Gamma-ray Burst Monitor during its most prolific activity