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GCN Circular 7148

Subject

Swift-BAT refined analysis of short GRB 071227

Date

2007-12-28T00:44:50Z (16 years ago)

From

Takanori Sakamoto at NASA/GSFC <takanori@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/UMBC), M. Stamatikos (GSFC/ORAU),
J. Tueller (GSFC), T. Ukwatta (GWU)
(i.e. 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 071227 (trigger #299787)
(Sakamoto, et al., GCN Circ. 7147Not found
 
 
).  The BAT ground-calculated position is
RA, Dec = 58.132, -55.959 deg which is 
   RA(J2000)  = 3h 52m 31.8s 
   Dec(J2000) = -55d 57' 32" 
with an uncertainty of 1.7 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 48%.
 
The mask weighted light curve shows multiple peaks during ~2 sec 
duration of the burst.  T90 (15-350 keV) is 1.8 +- 0.4 sec (estimated 
error including systematics).  Therefore, this burst might be
classified as a short burst.  Additional BAT analysis (e.g. spectral
lag) is on-going, and will be presented later.  
 
The time-averaged spectrum from T-0.1 to T+1.9 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
0.99 +- 0.22.  The fluence in the 15-150 keV band is 2.2 +- 0.3 x 10^-07 erg/cm2.
The 1-sec peak photon flux measured from T-0.09 sec in the 15-150 keV band
is 1.6 +- 0.2 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level.