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GCN Circular 40894

Subject
GRB 250702F: Swift detection of a burst with an optical counterpart
Event
GRB 250702F
Date
2025-07-02T21:42:54Z (2 days ago)
From
Mike Siegel at PSU/Swift MOC <siegel@swift.psu.edu>
Via
N. J. Klingler (GSFC/UMBC/CRESSTII), A. D'Ai (INAF-IASFPA),
R. Gupta (NASA GSFC), A. Y. Lien (U Tampa), T. M. Parsotan (GSFC) and
M. H. Siegel (PSU) report on behalf of the Neil Gehrels Swift
Observatory Team:

At 21:06:43.27 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 250702F (trigger= 1329888).  Swift slewed immediately to the burst.
The BAT on-board calculated location is 
RA, Dec 212.933, +16.699 which is 
   RA(J2000) = 14h 11m 44s
   Dec(J2000) = 16d 41' 57"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a multi-peaked structure
with a duration of about 70 sec. The peak count rate was ~4000 counts/sec 
(15-350 keV), at ~38 sec after the trigger.

The XRT began observing the field at 21:08:11.7 UT, 88.5 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 212.9378, 16.7475 which is equivalent to:
   RA(J2000)  = 14h 11m 45.07s
   Dec(J2000) = +16d 44' 51.0"
with an uncertainty of 4.8 arcseconds (radius, 90% containment). This
location is 175 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.

The initial flux in the 2.5 s image was 5.48e-09 erg cm^-2 s^-1 (0.2-10
keV).

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 97 seconds after the BAT trigger. There is a candidate afterglow in
the rapidly available 2.7'x2.7' sub-image at
  RA(J2000)  =	14:11:44.69 = 212.93622
  DEC(J2000) = +16:44:55.0  =  16.74861
with a 90%-confidence error radius of about 0.74 arc sec. This position is 6.7
arc sec. from the center of the XRT error circle. The estimated magnitude is
15.85 with a 1-sigma error of about  0.14. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.017.

This burst is spatially and temporally coincident with the burst reported by Fermi GBM (GCN Circ. 40892Loading...
 
 ).

Burst Advocate for this burst is N. J. Klingler (noelklin AT umbc.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/)