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GCN Circular 9138

GRB 090417A: Swift-BAT refined analysis
2009-04-17T19:50:47Z (15 years ago)
Scott Barthelmy at NASA/GSFC <>
W. H. Baumgartner (GSFC/UMBC), S. D. Barthelmy (GSFC), 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),
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+261 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 090417A (trigger #349447)
(Mangano, et al., GCN Circ. 9133).  The BAT ground-calculated position is
RA, Dec = 34.993, -7.141 deg which is 
   RA(J2000)  =  02h 19m 58.3s 
   Dec(J2000) = -07d 08' 28.9" 
with an uncertainty of 2.8 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 30%.
The mask-weighted light curve shows a single peak starting at T-0.06 sec,
peaking at T+0.04 sec, and ending at T+0.09 sec.  There appears to be
no extended emmission out to T+55 sec, at which point the burst location
went out of the BAT FOV during a planned target slew.  T90 (15-350 keV)
is 0.072 +- 0.018 sec (estimated error including systematics).
The time-averaged spectrum from T-0.0 to T+0.1 sec is best fit by a power law
with an exponential cutoff.  This fit gives a photon index -0.65 +- 2.11, 
and Epeak of 40.3 +- 12.7 keV (chi squared 67.41 for 56 d.o.f.).  For this
model the total fluence in the 15-150 keV band is 1.9 +- 0.5 x 10^-8 erg/cm2
and the 1-sec peak flux measured from T-0.46 sec in the 15-150 keV band is
3.6 +- 1.0 ph/cm2/sec.  A fit to a simple power law gives a photon index
of 2.99 +- 0.36 (chi squared 77.85 for 57 d.o.f.).  All the quoted errors
are at the 90% confidence level. 
The results of the batgrbproduct analysis are available at
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