TITLE:   GCN CIRCULAR
NUMBER:  42843
SUBJECT: GRB 251126A: Swift detection of a burst
DATE:    25/11/26 19:26:44 GMT
FROM:    K.L. Page at U Leicester <klp5@leicester.ac.uk>

R. Caputo (GSFC), M. J. Moss (GSFC), K. L. Page (U Leicester) and
D. M. Palmer (LANL) report on behalf of the Neil Gehrels Swift
Observatory Team:

At 19:10:36 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 251126A (trigger=1417793).  Swift slewed immediately to the burst.
The BAT on-board calculated location is 
RA, Dec 99.910, +54.987 which is 
   RA(J2000) = 06h 39m 39s
   Dec(J2000) = +54d 59' 13"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a complex
structure with a duration of about 20 sec.  The peak count rate
was ~2600 counts/sec (15-350 keV), at ~0 sec after the trigger.

The XRT began observing the field at 19:11:58.3 UT, 81.7 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source located at RA, Dec 99.94124, 54.98591 which is equivalent
to:
   RA(J2000)  = 06h 39m 45.90s
   Dec(J2000) = +54d 59' 09.3"
with an uncertainty of 4.4 arcseconds (radius, 90% containment). This
location is 64 arcseconds from the BAT onboard position, within the BAT
error circle. This position may be improved as more data are received;
the latest position is available at https://www.swift.ac.uk/sper. No
spectrum from the promptly downlinked event data is yet available to
determine the column density.

There are no UVOT data available at this time. Analysis will be reported at a later time.

Burst Advocate for this burst is R. Caputo (regina.caputo AT 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/)