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GCN Circular 5443

GRB 060813: Refined analysis of the Swift-BAT burst
2006-08-14T02:43:49Z (18 years ago)
Scott Barthelmy at NASA/GSFC <>
J. Cummings (GSFC/UMBC), L. Barbier (GSFC), S. D. Barthelmy (GSFC),
E. Fenimore (LANL), N. Gehrels (GSFC), D. Hullinger (BYU-Idaho),
H. Krimm (GSFC/USRA), M. Koss (GSFC/UMD), C. Markwardt (GSFC/UMD),
A. Moretti (INAF-OAB), D. Palmer (LANL), A. Parsons (GSFC),
T. Sakamoto (GSFC/ORAU), G. Sato (GSFC/ISAS), M. Stamatikos (GSFC/ORAU),
J. Tueller (GSFC)
on behalf of the Swift-BAT team:

Using the data set from T-239 to T+543 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 060813 (trigger #224364)
(Moretti, et al., GCN Circ. 5442).  The BAT ground-calculated position is
RA,Dec = 111.890, -29.844 deg {7h 27m 33.6s, -29d 50' 40.2"} (J2000)
+- 0.6 arcmin, (radius, sys+stat, 90% containment).  The partial coding was 39%.
The mask-weighted lightcurve shows a roughly square-shaped peak starting
at T-1 sec and lasting until T+9 sec.  It is then followed a softer component,
roughly constant but weaker intensity, lasting out to ~T+30 sec.
T90 (15-350 keV) is 14.9 +- 0.5 sec (estimated error including systematics).
The time-averaged spectrum from T-0.5 to T+27.8 is best fit by a power law
with an exponential cutoff.  This fit gives a photon index 1.00 +- 0.19, 
and a poorly-constrained Epeak of 176 +- 83 keV (chi squared 35.17 for 56 d.o.f.).
For this model the total fluence in the 15-150 keV band is
5.5 +- 0.1 x 10^-6 erg/cm2 and the 1-sec peak flux measured
from T+3.59 sec in the 15-150 keV band is 9.0 +- 0.4 ph/cm2/sec.
A fit to a simple power law gives a photon index of 1.35 +- 0.04
(chi squared 45.73 for 57 d.o.f.).  All the quoted errors are at the 90%
confidence level.
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