GCN Circular 13618

B.-B. Zhang (PSU), S. D. Barthelmy (GSFC), N. Gehrels (NASA/GSFC),
C. Gronwall (PSU), J. A. Kennea (PSU), H. A. Krimm (CRESST/GSFC/USRA)
and D. M. Palmer (LANL) report on behalf of the Swift Team:

At 02:35:18 UT, the Swift Burst Alert Telescope (BAT) triggered and
located a possible GRB (120811A, trigger=530581).  Swift did not slew to
the location.  The BAT on-board calculated location is 
RA, Dec 257.183, -22.736 which is 
   RA(J2000)  =  17h 08m 44s
   Dec(J2000) = -22d 44' 08"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows a single peak
with a duration of about 30 sec.  The peak count rate
was ~2500 counts/sec (15-350 keV), at ~0 sec after the trigger. 

This source was matched to a source 4U 1708-23 (== X Oph X-2)
in the on-board catalog, with an offset from 
the catalog position of 6 arcminutes.  However, the latest
position available is from the 1972 UHURU catalog, which has
a large position uncertainty consistent with this offset. 

At this time we cannot determine whether this is a GRB,
the catalogued 4U 1708-23, or some previously-unknown
Galactic transient. 

Burst Advocate for this burst is B.-B. Zhang (bbzhang AT psu.edu). 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/too.html.)