GCN Circular 7156
Subject
Further Swift-BAT analysis of GRB 071227
Date
2007-12-28T20:22:04Z (16 years ago)
From
Takanori Sakamoto at NASA/GSFC <Taka.Sakamoto@nasa.gov>
T. Sakamoto (GSFC/UMBC), J. Norris (NASA/Ames), T. Ukwatta (GWU),
S. D. Barthelmy (GSFC), N. Gehrels (GSFC), M. Stamatikos (GSFC/ORAU)
We further report about the additional analysis of the spectral
lag and the extended emission for a possible short GRB 071227.
Now, we believe GRB 071227 is very likely a short GRB based on
following the BAT prompt emission properties.
1) The spectral lag in 25-50 to 100-350 keV bands is consistent with
zero, 0.4 ms +- 14 ms, for 8 ms binning.
2) T90 of the initial spike is 1.8 +- 0.4 sec (Sato et al., GCN 7148)
which is in the 'short' range of the BAT burst duration (see figure 9
of the BAT1 catalog paper; Sakamoto et al., ApJS in press, arXiv:0707.4626).
3) We found a hint of the extended emission up to T+~100 sec
(Norris et al., ApJ, 643, 266). Although the significance in the image
domain is ~4 sigma (15-25 keV), we think this emission is associated with
the GRB because of no bright hard X-ray source in the BAT field of view
after the spacecraft slew which could be a source of a weak extended emission.