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GCN Circular 9289

Subject

GRB 090429A: Swift-BAT refined analysis

Date

2009-04-29T11:56:38Z (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), H. A. Krimm (GSFC/USRA),
C. B. Markwardt (GSFC/UMD), D. M. Palmer (LANL), A. M. Parsons (GSFC),
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-61 to T+302 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 090429A (trigger #350853)
(Markwardt, et al., GCN Circ. 9280Not found
 
 
).  The BAT ground-calculated position is
RA, Dec = 90.573, -52.389 deg, which is 
   RA(J2000)  =  06h 02m 17.5s 
   Dec(J2000) = -52d 23' 19.0" 
with an uncertainty of 1.7 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 100%.
 
The mask-weighted light curve shows a relatively smooth structure
with a couple overlapping peaks starting at ~T-12 sec and peaking at T_zero.
The main peak ends around T+40 sec with a long weak tail extending out
to ~T+200 sec.  T90 (15-350 keV) is 188 +- 37 sec (estimated error
including systematics).
 
The time-averaged spectrum from T-10.8 to T+203.0 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.55 +- 0.22.  The fluence in the 15-150 keV band is 1.0 +- 0.2 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T-0.35 sec in the 15-150 keV band
is 0.6 +- 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/350853/BA/