GCN Circular 6788
Subject
GRB 070809: The Swift evidence for the SHB nature of this burst
Event
Date
2007-09-13T21:00:38Z (18 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
S.D. Barthelmy (GSFC), T. Sakamoto (GSFC), J. Norris (SLAC), N. Gehrels (GSFC)
report:
GRB 070809 (Marshall GCN 6728 and Krimm GCN 6732) is very likely
a short burst. We base this on four results:
1) The spectral lag in 25-50 to 100-350 keV bands is consistent with zero:
+11 ms +38-61 ms for 8 ms binning.
2) The T90 was 1.3 +- 0.1 sec which is in the 'short' range
of BAT burst durations (see figure 9 of the BAT1 catalog paper; Sakamoto et al.,
accepted in ApJS, arXiv:0707.4626)
3) The fluence hardness ratio S(50-100 keV)/S(25-50 keV) is
1.24 +- 0.27 (90% error), which is consistent with the BAT short GRB
population (see figure 10 of the BAT1 catalog paper; Sakamoto et al.,
accepted in ApJS, arXiv:0707.4626).
4) The XRT light curve showed a flat phase often seen with long bursts.
However, some short bursts also have such a phase (GRB 050724 and 051221A).