TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  3305
SUBJECT: GRB 050421: Swift-BAT refined analysis
DATE:    05/04/21 15:44:53 GMT
FROM:    Louis M Barbier at NASA/GSFC/Swift  <lmb@cosmicra.gsfc.nasa.gov>

T. Sakamoto (GSFC/NRC), L. Barbier (GSFC), S. Barthelmy (GSFC), 
J. Cummings (GSFC/NRC), E. Fenimore (LANL), N. Gehrels (GSFC), 
D. Hullinger (UMD), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD),
T. Mitani (ISAS), D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/NRC), 
G. Sato (ISAS), M. Suzuki (Saitama), J. Tueller (GSFC), 
on behalf of the Swift/BAT team:

At 04:11:52 UT Swift-BAT detected GRB 050421 (trigger=115135)
(GCN Circ 3296, Barbier et al.).  The refined BAT ground position
is (RA,Dec) = 307.306, +73.665, [deg; J2000] +- 3.4 arcmin, (95%
containment).  The partial coding was 91%.  

The light curve has a FRED structure with a rise in < 1 second and a decay
in ~10 seconds.  T90 (15-350 keV) is (10.3 +- 2) seconds 
(estimated error including systematics).  

The photon index of the time-averaged spectrum is 1.7 +-0.4.  
The fluence in the 15-350 keV band is (1.8 +- 0.7 ) x 10^-7 erg/cm2.  
The 1-s peak photon flux measured from T0+1.4 seconds in the 15-350 
keV band and is (0.5 +- 0.1) ph/cm2/s.  All the quoted errors are at the 90% 
confidence level.