Count rates in different energy ranges showing the short hard spike and the longer soft tail in GRB 150101B. All ranges include counts in the NaI detectors; the counts in the BGO detectors are included only in the highest energy range. The short hard spike is visible above 50 keV. The soft tail is obvious in the 10–50 keV channel. GRB 150101B triggered GBM on the 16 ms timescale corresponding to the main peak, which places T0 at the end of this interval. The background count rates around trigger time are flat and well behaved; the background levels shown here are the time-averaged values around the trigger.