[vsnet-grb-info 4133] GRB 061218, Swift-BAT refined analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  5940
SUBJECT: GRB 061218, Swift-BAT refined analysis
DATE:    06/12/19 00:32:19 GMT
FROM:    Jay R. Cummings at NASA/GSFC/Swift  <jayc at 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.