[AAVSO-HEN] GRB 081211B(?): Possible burst detection from Swift-BAT slew data

[grb at aavso.org]

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TITLE:   GCN CIRCULAR
NUMBER:  8661
SUBJECT: GRB 081211B(?): Possible burst detection from Swift-BAT slew data
DATE:    08/12/12 04:06:51 GMT
FROM:    Antonio Copete at Harvard U  <acopete at head.cfa.harvard.edu>

A. Copete, J. Grindlay (Harvard)
S. Barthelmy, C. Markwardt, N. Gehrels (NASA/GSFC)

We report the detection of a likely GRB candidate by the BAT Slew  
Survey (BATSS) in the slew that started on 12/11/08 at 06:15:02 UT and  
lasted 121 sec. The ground-calculated position is RA, Dec = 168.231,  
+53.845 deg, which is
   RA (J2000) =  11h 12m 55s
   Dec(J2000) = +53d 50' 43"
with an uncertainty of 3.04 arcmin (90% confidence, including  
systematics). The detection was triggered by simultaneous detections  
of 7.4 sigma and 8.3 sigma from imaging in the overlapping energy  
bands of 15-50 keV and 15-150 keV, respectively. The burst mask-tagged  
lightcurve in the 15-150keV band shows two possible broad peaks in its  
emission profile that span the entire 102 sec that the source remains  
within the BAT field-of-view, starting at T+18 sec, and peaking T+34  
and T+69 sec, suggesting that this is possibly the tail end of the  
prompt emission of a burst at that location.

The time-averaged spectrum over the 102 sec of exposure of the source  
is best fit by a simple power law with photon index 1.73, and the  
fluence in the 15-150 keV band is 6.1 x 10^-7 erg/cm^2

A follow-up Swift ToO observation has been scheduled to begin on  
12/12/08 at 04:51 UT, 22.6 hours after the burst.
Optical/IR observations of this potential GRB are encouraged  
immediately, as it is well positioned for northern hemisphere observers.