TITLE:   GCN CIRCULAR
NUMBER:  37859
SUBJECT: GRB 241025A: Swift detection of a burst with an optical counterpart
DATE:    24/10/25 01:46:15 GMT
FROM:    David Palmer at LANL <palmer@lanl.gov>

E. Ambrosi (INAF-IASFPA), A. D'Ai (INAF-IASFPA),
V. D'Elia (SSDC & INAF-OAR), R. Gupta (NASA GSFC), J. A. Kennea (PSU),
D. M. Palmer (LANL), T. M. Parsotan (GSFC) and
B. Sbarufatti (INAF-OAB) report on behalf of the Neil Gehrels Swift
Observatory Team:

At 01:36:50 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 241025A (trigger=1262165).  Swift slewed immediately to the burst.
The BAT on-board calculated location is 
RA, Dec 333.330, +83.566 which is 
   RA(J2000) = 22h 13m 19s
   Dec(J2000) = +83d 33' 59"
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 180 sec.  The peak count rate
was ~1800 counts/sec (15-350 keV), at ~2 sec after the trigger.

The XRT began observing the field at 01:38:46.2 UT, 115.7 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 333.6488, 83.5739 which is equivalent to:
   RA(J2000)  = 22h 14m 35.71s
   Dec(J2000) = +83d 34' 26.0"
with an uncertainty of 4.8 arcseconds (radius, 90% containment). This
location is 131 arcseconds from the BAT onboard position, within the
BAT error circle. No event data are yet available to determine the
column density using X-ray spectroscopy.

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 125 seconds after the BAT trigger. There is a candidate afterglow in
the rapidly available 2.7'x2.7' sub-image at
  RA(J2000)  =	22:14:36.91 = 333.65379
  DEC(J2000) = +83:34:32.3  =  83.57565
with a 90%-confidence error radius of about 0.62 arc sec. This position is 6.6
arc sec. from the center of the XRT error circle. The estimated magnitude is
17.56 with a 1-sigma error of about  0.14. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.249.

Burst Advocate for this burst is E. Ambrosi (elena.ambrosi AT inaf.it).
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/)