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GCN Circular 8769

Subject
GRB 090102: Swift-BAT refined analysis
Date
2009-01-02T16:35:19Z (15 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
T. Sakamoto (GSFC/UMBC), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC),
J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC),
H. A. Krimm (GSFC/USRA), V. Mangano (INAF-IASFPA), C. B. Markwardt (GSFC/UMD),
D. M. Palmer (LANL), 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-239 to T+963 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 090102 (trigger #338895)
(Mangano, et al., GCN Circ. 8762).  The BAT ground-calculated position is
RA, Dec = 128.248, 33.107 deg, which is 
   RA(J2000)  =  08h 32m 59.5s 
   Dec(J2000) = +33d 06' 25.7" 
with an uncertainty of 1.4 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 6%.
 
The mask-weighted light curve shows approximately 4 overlapping peaks
starting at ~T-14 sec, peaking at ~T+2 sec, and ending at ~T+15 sec.
T90 (15-350 keV) is 27.0 +- 2.2 sec (estimated error including systematics).
 
The time-averaged spectrum from T-13.9 to T+18.7 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.36 +- 0.08.  The fluence in the 15-150 keV band is 6.8 +- 0.3 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+1.68 sec in the 15-150 keV band
is 5.5 +- 0.8 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/338895/BA/
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