Left: the light curve of GRB 080928 as seen by Swift/BAT. Swift triggered at the gamma-ray peak at t₀ = 0, which was followed by at least two more peaks with the maximum at t₀ + 204 s. There may be a faint precursor of the main burst at t₀ − 90 s. Right: Fermi/GBM light curve of the NaI detectors #0, #3, #4, and #7 combined with 2 s resolution (black line) and 0.256 s resolution (gray line). A zoom into the 64 ms-binned, background-subtracted light curve around the peak is shown in the inset. Variability on time scales of  ~128 ms is detected at 3σ (solid gray line) above the background plus shot noise fluctuations. In this figure the time zero-point is the Fermi/GBM trigger time t_0,GBM (Eq. (1)).