TITLE: GCN CIRCULAR NUMBER: 11870 SUBJECT: GRB 110402A: Spectral lag indicates short hard burst DATE: 11/04/03 00:24:08 GMT FROM: Scott Barthelmy at NASA/GSFC S.D. Barthelmy (GSFC) and J. Norris (BSU) report: For GRB 110402A (Trigger 450545, GCNs 11857 & 11866), the spectral lag analysis of the Swift-BAT data from T+0.8 sec to T+6.0 sec (the initial 5 spikes), yields a lag of 3.7 +2.5/-2.9 msec for the 25-50 to 100-300 keV bands using a lightcurve binning of 4 msec. While the 5.2 sec duration for the 5 spikes is formally beyond the cononical 2-s boundary in duration for short bursts, the small lag value favors a short burst identification. We note that there is on-going, much softer emission from T+5 to T+78 sec, and lacking sufficient structure to yield a significant lag measurement.