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GCN Circular 9393

Subject

GRB 090518, Swift-BAT refined analysis

Date

2009-05-18T15:29:11Z (16 years ago)

From

Takanori Sakamoto at NASA/GSFC <takanori.sakamoto-1@nasa.gov>

J. R. Cummings (GSFC/UMBC), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), 
E. E. Fenimore (LANL), N. Gehrels (GSFC), 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),
J. Tueller (GSFC), T. N. Ukwatta (GWU)
(i.e. the Swift-BAT team):
 
Using the data set from T-119 to T+963 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 090518 (trigger #352420)
(Evans, et al., GCN Circ. 9386Loading...
 
 ).  The BAT ground-calculated position is
RA, Dec = 119.957, 0.778 deg which is 
   RA(J2000)  =  07h 59m 49.6s 
   Dec(J2000) = +00d 46' 41.4" 
with an uncertainty of 1.2 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 75%.
 
The mask-weighted light curve shows a FRED-like peak starting at T-0.5 sec, 
peaking at T+0 sec, and ending at T+3 sec.  T90 (15-350 keV) is 
6.9 +- 1.7 sec (estimated error including systematics).
 
The time-averaged spectrum from T-2.4 to T+6.9 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.54 +- 0.14.  The fluence in the 15-150 keV band is 4.7 +- 0.4 x 10^-07 erg/cm2.
The 1-sec peak photon flux measured from T-0.08 sec in the 15-150 keV band
is 2.4 +- 0.2 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/352420/BA/