[vsnet-grb-info 7736] GRB 090429B: Swift-BAT refined analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  9290
SUBJECT: GRB 090429B: Swift-BAT refined analysis
DATE:    09/04/29 12:09:35 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott at lheamail.gsfc.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), 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-60 to T+243 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 090429B (trigger #350854)
(Ukwatta, et al., GCN Circ. 9281).  The BAT ground-calculated position is
RA, Dec = 210.672, 32.167 deg, which is 
   RA(J2000)  =  14h 02m 41.2s 
   Dec(J2000) = +32d 10' 02.0" 
with an uncertainty of 1.3 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 84%.
 
The mask-weighted light curve shows a main peak starting at ~T-4 sec,
peaking at ~T-0.1 sec, and ending around T+3 sec.  There are two very
weak peaks: ~T+30 to ~T+70 sec, and ~T+100 to ~T+110 sec.
T90 (15-350 keV) is 5.5 +- 1.0 sec (estimated error including systematics).
 
The time-averaged spectrum from T-4.5 to T+2.4 sec is best fit by a power law
with an exponential cutoff.  This fit gives a photon index 0.47 +- 0.77, 
and Epeak of 42.1 +- 5.6 keV (chi squared 29.6 for 56 d.o.f.).  For this
model the total fluence in the 15-150 keV band is 3.1 +- 0.3 x 10^-7 erg/cm2
and the 1-sec peak flux measured from T-0.28 sec in the 15-150 keV band is
1.6 +- 0.2 ph/cm2/sec.  A fit to a simple power law gives a photon index
of 1.96 +- 0.13 (chi squared 45.3 for 57 d.o.f.).  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/350854/BA/