[vsnet-grb-info 7263] Trigger 340734: Swift detection of a possible short burst

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  8834
SUBJECT: Trigger 340734: Swift detection of a possible short burst
DATE:    09/01/22 08:01:26 GMT
FROM:    David Palmer at LANL  <palmer at lanl.gov>

D. Grupe (PSU), W. H. Baumgartner (GSFC/UMBC), S. Campana (INAF-OAB),
P. A. Evans (U Leicester), C. Gronwall (PSU), J. A. Kennea (PSU),
D. M. Palmer (LANL), J. L. Racusin (PSU) and L. Vetere (PSU) report
on behalf of the Swift Team:

At 07:30:06 UT, the Swift Burst Alert Telescope (BAT) triggered and
located a possible GRB (trigger=340734).  Swift slewed immediately to 
the calculated location.  The BAT on-board calculated location is 
RA, Dec 263.343, -60.135 which is 
   RA(J2000) = 17h 33m 22s
   Dec(J2000) = -60d 08' 05"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a single peak 
with a duration of about 0.5 sec.  The peak count rate
was ~2000 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 07:31:09.3 UT, 63.5 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 150 seconds with the White
filter  starting 66 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. Because of
the density of catalogued stars, further  analysis is required to
report an upper limit for any afterglow in the  sub-image. The
coverage of the BAT error circle by the 8'x8' region is 100%. Because
of the density of catalogued stars, further analysis is required to
report an upper limit for any afterglow in the region. No correction
has been made for the expected extinction corresponding to E(B-V) of
0.07. 

This trigger had a light curve duration and intensity
similar to the SGR bursts from the newly reactivated
AXP 1E1547.0-5408 (GCN 8833).  The peak found in the image
at the above location is of marginal significance. 
There is no XRT source found in the immediately available TDRSS
data.  For these reasons, it is possible that this trigger
is due to a rate trigger due the AXP followed by a fluctuation
in the image domain.  Confirmation of the reality of this
possible GRB will require analysis of the full dataset from Malindi. 

Burst Advocate for this burst is D. Grupe (grupe AT astro.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.)