  SGR J1550-5418 exhibited three active bursting episodes in 2008 October and
in 2009 January and March, emitting hundreds of typical Soft Gamma Repeater
(SGR) bursts in soft gamma-rays. The second episode was especially intense, and
our untriggered burst search on Fermi/GBM data (8-1000 keV) revealed ~450
bursts emitted over 24 hours during the peak of this activity. Using the GBM
data, we identified a ~150-s-long enhanced persistent emission during 2009
January 22 that exhibited intriguing timing and spectral properties: (i) clear
pulsations up to ~110 keV at the spin period of the neutron star, (ii) an
additional (to a power-law) blackbody component required for the enhanced
emission spectra with kT ~ 17 keV, (iii) pulsed fraction that is strongly
energy dependent and highest in the 50-74 keV energy band. A total
isotropic-equivalent energy emitted during this enhanced emission is estimated
to be 2.9 x 10^{40}(D/5 kpc)^2 erg. The estimated area of the blackbody
emitting region of ~0.046(D/5 kpc)^2 km^2 is the smallest "hot spot" ever
measured for a magnetar and most likely corresponds to the size of
magnetically-confined plasma near the neutron star surface.
