GCN Circular 5940
Subject
GRB 061218, Swift-BAT refined analysis
Date
2006-12-19T00:32:19Z (17 years ago)
From
Jay R. Cummings at NASA/GSFC/Swift <jayc@milkyway.gsfc.nasa.gov>
G. Sato (GSFC/ISAS), 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), D. Palmer (LANL),
A. Parsons (GSFC), T. Sakamoto (GSFC/ORAU), M. Stamatikos (GSFC/ORAU),
J. Tueller (GSFC), S. Zane (UCL-MSSL)
on behalf of the Swift-BAT team:
Using the data set from T-120 to T+183 sec from the recent telemetry
downlink, we report further analysis of BAT GRB 061218 (trigger
#251863) (Zane, et al., GCN Circ. 5936). The BAT ground-calculated
position is RA, Dec = 149.238, -35.221 deg which is
RA(J2000) = 09h 56m 57.0s
Dec(J2000) = -35d 13' 15.9"
with an uncertainty of 4 arcmin, (radius, sys+stat, 90% containment).
The burst was in the fully-coded field of view.
The mask-weighted lightcurve consists of a single very weak pulse
lasting about 7 sec. T90 (15-350 keV) is 4.1 +- 0.5 sec (estimated
error including systematics).
The time-averaged spectrum from T+0.0 to T+4.1 is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
2.76 +- 0.63. The fluence in the 15-150 keV band is 4.1 +- 1.5 x 10^-8 erg/cm2.
The 1-sec peak photon flux measured from T+0.00 sec in the 15-150 keV band
is 0.2 +- 0.1 ph/cm2/sec. All the quoted errors are at the 90% confidence level.