[vsnet-grb-info 6370] Trigger 317393: Swift detection of a possible GRB

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  7986
SUBJECT: Trigger 317393: Swift detection of a possible GRB
DATE:    08/07/20 00:49:46 GMT
FROM:    David Palmer at LANL  <palmer at lanl.gov>

J. K. Cannizzo (NASA/UMBC), D. N. Burrows (PSU),
N. Gehrels (NASA/GSFC), C. Gronwall (PSU), C. Guidorzi (INAF-OAB),
S. T. Holland (CRESST/USRA/GSFC), C. B. Markwardt (CRESST/GSFC/UMD),
C. Pagani (PSU), D. M. Palmer (LANL), T. N. Ukwatta (GSFC/GWU) and
P. A. Ward (MSSL-UCL) report on behalf of the Swift Team:

At 00:23:41 UT, the Swift Burst Alert Telescope (BAT) triggered and
located a possible GRB (trigger=317393).  Swift slewed immediately to 
the location.  The BAT on-board calculated location is 
RA, Dec 162.521, -10.495 which is 
   RA(J2000) = 10h 50m 05s
   Dec(J2000) = -10d 29' 42"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  As is usual for a 64-second image trigger,
there is no obvious variation in the immediately available light curve. 

The XRT began observing the field at 00:26:12.4 UT, 151.3 seconds after
the BAT trigger. No source was detected in the promptly available XRT
data. We are waiting for the full dataset to detect and localise the
XRT counterpart. 

UVOT took a finding chart exposure of 100 seconds with the White
(160-650 nm)  filter starting 98 seconds after the BAT trigger. No
afterglow candidate has  been found in the initial data products. The
typical 3-sigma upper limit has been about 18.5 mag.  The 8'x8' region
for the list of sources generated on-board covers 100% of the BAT
error circle. The list of sources is typically complete to about 18
mag. No correction has been made for extinction. 

Based on the marginal significance of the BAT detection, and the
lack of an XRT or UVOT detection, we cannot confirm the reality of this source. 
We note, however, that the source 1RXS J105002.8-103240 is located at
the edge of the BAT error circle.  More information will be available 
following the next downlink at about 0120 UT. 

Burst Advocate for this burst is J. K. Cannizzo (cannizzo AT milkyway.gsfc.nasa.gov). 
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.)