GCN Circular 4321
S. Barthelmy (GSFC), J. Cummings (GSFC/NRC), N. Gehrels (GSFC), J. Norris (GSFC), D. Palmer (LANL), A. Parsons (GSFC) on behalf of the Swift-BAT team: The BAT team now believes this burst to be definitely short. The formal T90 value is 1.2 +/- 0.2 sec (Sato, Circ 4318). The 6-sec_duration statement in our 1st circ (Mangano, Circ 4315) was based on a non-background-subtracted raw TDRSS lightcurve. We now have the mask-tagged lightcurve with a ground energy scale calibration applied to the events, and the 2nd peak at T+6 sec is not present (it may be attributable to a background fluctuation or noisy detector(s)). We further note that the peak at T0 is resolved into 3 separate peaks which is not uncommon in the BATSE short bursts. The spectral lag (Norris & Bonnell, submitted to ApJ) for this burst is -0.0010 sec (+0.0150 -0.0170 sec); very typical for short bursts. Swift-XRT & UVOT follow-up observations are continuing and we encourage other follow-up observations on this short burst.