GCN Circular 39182

M. Ferro (INAF-OAB), R. Gupta (NASA GSFC), J. A. Kennea (PSU),
K. L. Page (U Leicester) and B. Sbarufatti (INAF-OAB) report on behalf
of the Neil Gehrels Swift Observatory Team:

At 01:16:07 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 250207A (trigger=1287821).  Swift slewed immediately to the burst.
The BAT on-board calculated location is 
RA, Dec 16.115, -12.159 which is 
   RA(J2000) = 01h 04m 28s
   Dec(J2000) = -12d 09' 30"
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 30 sec.  The peak count rate
was ~3847 counts/sec (15-350 keV), at ~6 sec after the trigger.

The XRT began observing the field at 01:17:53.2 UT, 105.9 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 16.0892, -12.1633 which is equivalent to:
   RA(J2000)  = 01h 04m 21.41s
   Dec(J2000) = -12d 09' 47.9"
with an uncertainty of 5.9 arcseconds (radius, 90% containment). This
location is 92 arcseconds from the BAT onboard position, within the BAT
error circle. Despite the onboard localisation, no X-ray source was
detected in 85 s of promptly-downlinked data, suggesting that the
initial centroid may equally have been a cosmic ray. This position
should	therefore be treated with caution. 

The initial flux in the 2.5 s image was 7.54e-10 erg cm^-2 s^-1 (0.2-10
keV).

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 113 seconds after the BAT trigger. There is a candidate afterglow in
the rapidly available 2.7'x2.7' sub-image at
  RA(J2000)  =	01:04:21.41 =  16.08919
  DEC(J2000) = -12:09:52.5  = -12.16458
with a 90%-confidence error radius of about 0.74 arc sec. This position is 4.6
arc sec. from the center of the XRT error circle. The estimated magnitude is
15.04 with a 1-sigma error of about  0.14. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.027.

Burst Advocate for this burst is M. Ferro (matteo.ferro 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/)