[vsnet-grb-info 23973] Swift Trigger 931384: possible GRB 191025A

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  26072
SUBJECT: Swift Trigger 931384: possible GRB 191025A
DATE:    19/10/25 03:23:10 GMT
FROM:    Kim Page at U.of Leicester  <klp5 at leicester.ac.uk>

A. P. Beardmore (U Leicester), J.D. Gropp (PSU), J. A. Kennea (PSU),
K. L. Page (U Leicester), B. Sbarufatti (PSU), M. H. Siegel (PSU) and
A. Tohuvavohu (Toronto) report on behalf of the Neil Gehrels Swift
Observatory Team:

At 02:46:47 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 191025A (trigger=931384).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 320.755, -48.330 which is 
   RA(J2000) = 21h 23m 01s
   Dec(J2000) = -48d 19' 46"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty). The significance is relatively low in both 
the rate and image domains. 

The XRT began observing the field at 02:48:08.9 UT, 82.0 seconds after
the BAT trigger. No source was detected in 1.5 ks of promptly
downlinked 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 85 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 19.6 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 the expected extinction corresponding to
E(B-V)  of 0.03. 

Due to the low significance of the BAT trigger and the lack of immediate
counterpart detection in the XRT or UVOT, the Swift team will not be able to
confirm or deny whether this event is a GRB without further data. 

Burst Advocate for this burst is A. P. Beardmore (apb AT star.le.ac.uk). 
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/)