[vsnet-grb-info 17273] Subject: GRB 151122A: Swift detection of a burst

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  18637
SUBJECT: Subject: GRB 151122A: Swift detection of a burst 
DATE:    15/11/23 20:25:59 GMT
FROM:    David Palmer at LANL  <palmer at lanl.gov>

David Palmer reports on behalf of the Swift team:

On November 22, at 17:00:40 UT, BAT rate-triggered and detected a 6.0 sigma 
peak in an image. Because this was below the nominal 6.5 sigma threshold, 
BAT did not trigger a burst response.  However, ground analysis leads us to 
believe that this is a real burst, GRB 151122A (trigger #664653) with an
onboard-calculated location RA,dec = 299.704, -19.899, which is
RA(J2000) = 19h 58m 49s
dec(J2000) = -19d 53’ 56”
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The lightcurve shows a slow-rise, fast decay peak
from T-5 s to T+12 s, following by a possible second lower peak extending
to T+45 s.  The peak count rate was ~1500 counts/sec (15-350 keV), 
at ~6 sec after the trigger.

The peak of this burst was after a pre-planned slew had started, thus
only the initial rise of this burst was imaged on board.  However, the
burst was also seen by Fermi GBM (trigger #469904449) which
gave a final ground-calculated position of RA,dec = 292.950, -21.350
with an 11.1 degree statistical error radius and a 1-sigma location contour
that contains the BAT location.  The GBM lightcurve is also consistent with
the BAT lightcurve.  Therefore we believe that both of these triggers
are the same astrophysical GRB at the location found by BAT

A Target Of Opportunity Swift observation has been accepted for this GRB.