[vsnet-grb-info 2560] GRB 051227: Swift detection of a burst

[GCN Circulars]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  4397
SUBJECT: GRB 051227: Swift detection of a burst
DATE:    05/12/27 18:59:47 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <Scott at lheamail.gsfc.nasa.gov>

L. Barbier (GSFC), S. Barthelmy (GSFC), A. Beardmore (U Leicester),
D. Burrows (PSU), J. Cummings (GSFC/NRC), A. Falcone (PSU), N. Gehrels (GSFC),
K. Page (U Leicester), A. Retter (PSU), P. Roming (PSU),
T. Sakamoto (GSFC)
on behalf of the Swift team:

At 18:07:16 UT, Swift-BAT triggered and located GRB 051227 (trigger=174738).
The spacecraft slewed immediately.  The BAT on-board calculated location is
RA,Dec 125.270d,+31.929d {08h 21m 05s,+31d 55' 44"} (J2000), with an uncertainty
of 3 arcmin (radius, 90% containment, stat+sys).  The BAT light curve shows
a multi-peak structure with a total duration of at least 8 sec.  The peak count
rate was ~3500 counts/sec (15-350 keV), at 0 seconds after the trigger.

The XRT began observing the GRB at 18:08:49 UT, 93s after the BAT trigger.
A bright fading uncataloged source was found by the on-board centroiding
algorithm at:
 RA(J2000)=  08h 20m 57.6s
DEC(J2000)= +31d 55' 33.5"
with an uncertainty of 7 arcseconds radius (90% containment).  This position
has not been corrected for the XRT boresight and retains a 4-5 arcsecond
residual systematic error, which is included in the 7 arcsecond error radius.
This position lies 95 arcseconds from the centre of the BAT error circle.
The initial X-ray flux is estimated to be 1.1e-9 erg/cm2/sec (0.2-10keV).

UVOT took a finding chart exposure of nominal 200 seconds with the V filter
starting 96 seconds after the BAT trigger.  No afterglow candidate
has been found in the initial data products.  Image catalog data are not
available at this time.  The overlap of the 8'x8' region for the list
of sources generated on-board and the XRT error circle is uncertain.
No correction has been made for the expected visual extinction
of about 0.1 magnitudes.

We note that according to SIMBAD, there is a galactic cluster NSC J082047+315700
within 2.7 arcmin from this location, but this is definitely a long burst
(not a short GRB).