[vsnet-grb-info 7789] GRB 090509: Swift-BAT refined analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  9335
SUBJECT: GRB 090509: Swift-BAT refined analysis
DATE:    09/05/10 05:41:38 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott at lheamail.gsfc.nasa.gov>

J. Tueller (GSFC), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC),
J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC),
D. Grupe (PSU), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC/UMD),
D. M. Palmer (LANL), A. M. Parsons (GSFC), T. Sakamoto (GSFC/UMBC),
G. Sato (ISAS), M. Stamatikos (GSFC/ORAU), T. N. Ukwatta (GWU)
(i.e. the Swift-BAT team):
 
Using the data set from T-60 to T+243 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 090509 (trigger #351525)
(Grupe, et al., GCN Circ. 9325).  The BAT ground-calculated position is
RA, Dec = 241.426, -28.420 deg, which is 
   RA(J2000)  =  16h 05m 42.3s 
   Dec(J2000) = -28d 25' 12.6" 
with an uncertainty of 1.9 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 29%.
 
The mask-weighted light curve shows multiple overlapping peaks starting
at ~T-4 sec, peaking at ~T+21 sec, and ending at ~T=3 sec.
T90 (15-350 keV) is 20.4 +- 1.7 sec (estimated error including systematics).
 
The time-averaged spectrum from T-1.1 to T+22.4 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.54 +- 0.16.  The fluence in the 15-150 keV band is 1.1 +- 0.1 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+20.73 sec in the 15-150 keV band
is 1.5 +- 0.3 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level. 
 
The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/351525/BA/