[vsnet-grb-info 2380] GRB 051109: Swift-BAT refined analysis

[GCN Circulars]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  4217
SUBJECT: GRB 051109: Swift-BAT refined analysis
DATE:    05/11/09 04:25:01 GMT
FROM:    Takanori Sakamoto at NASA/GSFC  <takanori at milkyway.gsfc.nasa.gov>

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

Using the data set from T-60 to T+70 sec from the recent telemetry
downlink, we report further analysis of BAT GRB 051109 
(trigger #163136)  (Tagliaferri, et al., GCN 4213).  The BAT 
ground-calculated position is 
(RA,Dec) = 330.295, +40.836 {22h 01m 10.7s, +40d 50' 10.5"} [deg; J2000] 
+-2.1 arcmin, (radius, sys+stat, 90% containment).  The partial coding was 9%.  

The lightcurve has two peaks.  The initial strong peak starts at 
T-5 sec with a duration of 20 sec.  The second weaker peak starts 
at T+21 sec. with a duration of 20 sec.  T90 (15-350 keV) is (36 +- 2) sec 
(estimated error including systematics).  

The power law index of the time-averaged spectrum is 1.5 +- 0.2.  
The fluence in the 15-150 keV band is (2.1 +- 0.3) x 10^-6 erg/cm2.  
The 1-sec peak photon flux measured from T0+0.4 sec in the 15-150 keV 
band is (3.7 +- 0.7) ph/cm2/sec.  All the quoted errors are at the 90% 
confidence level.