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GCN Circular 9139

Subject
GRB 090417B: Swift-BAT refined analysis
Date
2009-04-17T23:31:58Z (15 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.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), T. Sakamoto (GSFC/UMBC),
G. Sato (ISAS), M. Stamatikos (GSFC/ORAU), B. Sbarufatti (INAF-IASFPA),
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 090417B (trigger #349450)
(Sbarufatti, et al., GCN Circ. 9135).  The BAT ground-calculated position is
RA, Dec = 209.624, 46.954 deg, which is 
   RA(J2000)  =  13h 58m 29.7s 
   Dec(J2000) = +46d 57' 14.1" 
with an uncertainty of 4.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 94%.
 
The mask-weighted light curve shows that this burst started before T-200 sec
(where we start collecting event data on each trigger), slowly rises
to a peak around T+400 sec and slowly decreases out past T+950 sec
(where we stop processing the data).  T90 (15-350 keV) is greater than 260 sec.
 
The time-averaged spectrum from T+278.7 to T+617.1 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.85 +- 0.14.  The fluence in the 15-150 keV band is 2.3 +- 0.2 x 10^-06 erg/cm2.
The 1-sec peak photon flux measured from T+434.93 sec in the 15-150 keV band
is 0.3 +- 0.1 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/349450/BA/
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