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GCN Circular 9123

Subject
GRB 090410: Swift-BAT refined analysis
Date
2009-04-10T23:59:04Z (15 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
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),
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 sets from T-240 to T+963 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 090410 (trigger #348929)
(Grupe, et al., GCN Circ. 9122).  The BAT ground-calculated position is
RA, Dec = 334.956, 15.419 deg, which is 
   RA(J2000)  =  22h 19m 49.4s 
   Dec(J2000) = +15d 25' 08.6" 
with an uncertainty of 1.8 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 100%.
 
The mask-weighted light curve shows two main peaks with some precursor activity.
The precursor activity starts at ~T-55 sec.  And because the target location
only came into the BAT FOV at T-110 sec, there may have been even earlier activity.
The first main peak started at ~T-10 sec, peaked at ~T+7 sec, and ended 
around T+45 sec.  The second main peak started at ~T+80 sec, peaked at ~T+120 sec,
and returned to baseline T+170 sec.  The burst location left the BAT FOV
at ~T+390 sec.  T90 (15-350 keV) is 165 +- 8 sec (estimated error
including systematics).
 
The time-averaged spectrum from T-49.2 to T+139.4 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.19 +- 0.05.  The fluence in the 15-150 keV band is 5.6 +- 0.2 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+8.90 sec in the 15-150 keV band
is 1.9 +- 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/348929/BA/
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