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GCN Circular 6778

GRB 070911, Swift-BAT refined analysis
2007-09-11T17:31:54Z (17 years ago)
Hans Krimm at NASA-GSFC <>
D. Palmer (LANL),  L. Barbier (GSFC), S. D. Barthelmy (GSFC),
J. Cummings (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC),
H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), A. Parsons (GSFC),
T. Sakamoto (GSFC/ORAU), G. Sato (GSFC/ISAS), M. Stamatikos (GSFC/ORAU),
J. Tueller (GSFC), T. Ukwatta (GWU) (i.e. the Swift-BAT team):

Using the data set from T-299 to T+303 sec from the recent telemetry downlink,
we report further analysis of BAT GRB  (trigger #290624)
(Krimm, et al., GCN Circ. 6777).  The BAT ground-calculated position is
RA, Dec = 25.819, -33.484 deg which is
    RA(J2000) = 1h 43m 16.5s
    Dec(J2000) = -33d 29' 3"
with an uncertainty of 1.5 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 88%.

The mask tagged light curve starts to rise at around T-70 sec and 
continues above
baseline until  T+160 sec.  The burst contains multiple strong peaks 
in a cluster
from T-5 to T+55 sec, then a drop in flux and another cluster of peaks from
T+85 to T+145 sec.The first cluster of peaks has a harder spectrum 
than the second.
T90 (15-350 keV) is 162 +- 10 sec (estimated error including systematics).

The time-averaged spectrum from -73.0 to  +158.8 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.72 +- 0.04.  The fluence in the 15-150 keV band is 1.2 +- 0.02 x 
10^-05 erg/cm2.
The 1-sec peak photon flux measured from T+36.13 sec in the 15-150 keV band
is 3.9 +- 0.2 ph/cm2/sec.  All the quoted errors are at the 90% confidence
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