[vsnet-grb-info 20117] GRB 171209A: Swift detection of a burst

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  22213
SUBJECT: GRB 171209A: Swift detection of a burst
DATE:    17/12/09 15:30:16 GMT
FROM:    David Palmer at LANL  <palmer at lanl.gov>

S. J. LaPorte (PSU), D. N. Burrows (PSU), P. D'Avanzo (INAF-OAB),
S. W. K Emery (UCL-MSSL), J.D. Gropp (PSU), J. A. Kennea (PSU),
N. P. M. Kuin (UCL-MSSL), A. Melandri (INAF-OAB) and
D. M. Palmer (LANL) report on behalf of the Swift Team:

At 14:46:16 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 171209A (trigger=796100).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 139.382, -30.528 which is 
   RA(J2000) = 09h 17m 32s
   Dec(J2000) = -30d 31' 38"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a multi-peaked
structure with a duration of about 100 sec.  The peak count rate
was ~1300 counts/sec (15-350 keV), at ~80 sec after the trigger. 

UVOT took a finding chart exposure of 194 seconds with the U filter starting
265 seconds after the BAT trigger. No credible afterglow candidate has been
found in the initial data products. The 2.7'x2.7' sub-image covers 25% of the
BAT error circle. The typical 3-sigma upper limit has been about 19.2 mag. The
8'x8' region for the list of sources generated on-board covers 98% of the BAT
error circle. The list of sources is typically complete to about 18.0 mag. No
correction has been made for the expected extinction corresponding to E(B-V) of
0.15. 
However, a possible candidate source of magnitude 17.3 in white is present at 
   RA(J2000) =  09h 17m 36.70s
   Dec(J2000) = -30d 31m 12.0s
which is very close to two other sources in the DSS survey image. 

The XRT detected the afterglow from this GRB.  However, due to data 
transmission problems, an XRT position will not be available until
more data is transmitted to the ground. 

Burst Advocate for this burst is S. J. LaPorte (extragsam AT gmail.com). 
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.)