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GCN Circular 8800

Subject
GRB 090111, Swift-BAT refined analysis
Date
2009-01-12T20:52:55Z (15 years ago)
From
Hans Krimm at NASA-GSFC <hans.krimm@nasa.gov>
M. Stamatikos (GSFC/ORAU), 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), C. B. Markwardt (GSFC/UMD), K. McLean (GSFC/UMD),
D. M. Palmer (LANL), A. M. Parsons (GSFC), T. Sakamoto (GSFC/UMBC),
G. Sato (ISAS), 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 the recent telemetry 
downlink,
we report further analysis of BAT GRB 090111 (trigger #339696)
(Sakamoto et al., GCN Circ. 8795).  The BAT ground-calculated position is
RA, Dec = 251.656, 0.067 deg which is
   RA(J2000)  =  16h 46m 37.4s
   Dec(J2000) = +00d 04' 01.5"
with an uncertainty of 1.4 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 82%.

The mask-weighted light curve shows two peaks of roughly equal intensity.
The first lasts from T-3 sec to T+9 sec and the second from T+10 to T+26 
seconds.
T90 (15-350 keV) is 24.8 +- 2.7 sec (estimated error including 
systematics).

The time-averaged spectrum from T-2.9 to T+25.6 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
2.37 +- 0.17.  The fluence in the 15-150 keV band is 6.2 +- 0.6 x 10-7 
erg/cm2.
The 1-sec peak photon flux measured from T+10.70 sec in the 15-150 keV band
is 0.9 +- 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/339696/BA/
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