TITLE:   GCN CIRCULAR
NUMBER:  9475
SUBJECT: GRB 090531B: Swift/BAT spectral lag results
DATE:    09/06/01 15:55:43 GMT
FROM:    Tilan Ukwatta at GSFC/GWU  <tilan.ukwatta@gmail.com>

T. N. Ukwatta (GWU/GSFC), S. D. Barthelmy (GSFC), J. R. Cummings
(NASA/UMBC), T. Sakamoto (GSFC/UMBC), M. Stamatikos (GSFC/ORAU),
N. Gehrels (GSFC) (for the Swift-BAT team):

For GRB 090531B (Cummings et al. GCN 9461), the BAT team has
analyzed spectral lags for the data from T-1.0 sec to T+2.0 sec
using non-mask weighted light curves with 16 msec time binning.
The spectral lags were measured between standard canonical BAT
energy bands: channel 1 (15-25 keV), 2 (25-50 keV), 3 (50-100 keV)
and 4 (100-350 keV) are given below.

Lag Ch3-Ch2 : -2 +/- 9 msec
Lag Ch4-Ch2 : 11 +/- 5 msec
Lag Ch4-Ch3 :  8 +/- 3 msec

The signal-to-noise ratio in channel 1 is too weak to make a
lag measurement.

These lag values are consistent with lags observed for short
hard burst with extended emission.