GCN Circular 6158

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), C. Pagani (PSU), 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-2.0 to T+8.1 sec, we report further analysis 
of BAT GRB 070227 (trigger #262347)  (Pagani, et al., GCN Circ. 6156
Not found
 
 
).  
The BAT ground-calculated position is RA, Dec = 120.566, -46.305 (J2000)
  RA:  +08h 02m 16s
  Dec: -46d 18' 17"
with an uncertainty of 2.5 arcmin, (radius, sys+stat, 90% containment).  
The partial coding was 3%.  Because this was a failed trigger on-board, 
this is all the detailed BAT data we are going to get on this burst.
 
The burst had two weak overlapping peaks with spectral evolution. The
larger peak was at T+1 and the smaller at T+6 sec.  There is no 
additional strong emission at times later than T+8, but we cannot rule 
out weak emission.  T90 (15-350 keV) is 7 +- 2 sec (estimated error 
including systematics).
 
The time-averaged spectrum from T+0.0 to T+8.0 is best fit by a simple 
power-law model.  The power law index of the time-averaged spectrum is 
1.54 +- 0.27.  The fluence in the 15-150 keV band is 
1.6 +- 0.2 x 10^-06 erg/cm2.  The 1-sec peak photon flux measured from 
T+0.00 sec in the 15-150 keV band is 2.7 +- 0.4 ph/cm2/sec.  The quoted 
errors are at the 90% confidence level considering the statistical and
usual systematic effects.  However, because of the extreme partial coding
of this burst, and particularly the reduced sensitivity to low energy
photons at the edge of the FOV, we expect an extra systematic uncertainty
contribution of about 10%.