GCN Circular 42924

M. J. Moss (GSFC), S. Dichiara (PSU), R. Gupta (NASA GSFC),
J. A. Kennea (PSU), K. L. Page (U Leicester) and T. M. Parsotan (GSFC)
report on behalf of the Neil Gehrels Swift Observatory Team:

At 16:26:30 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 251201B (trigger=1418729).  Swift slewed immediately to the burst.
The BAT on-board calculated location is 
RA, Dec 6.409, -44.237 which is 
   RA(J2000) = 00h 25m 38s
   Dec(J2000) = -44d 14' 12"
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 40 sec.  The peak count rate
was ~2000 counts/sec (15-350 keV), at ~0 sec after the trigger.

The XRT began observing the field at 16:28:03.7 UT, 93.4 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 6.3925, -44.2312 which is equivalent to:
   RA(J2000)  = 00h 25m 34.20s
   Dec(J2000) = -44d 13' 52.3"
with an uncertainty of 7.0 arcseconds (radius, 90% containment). This
location is 47 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 0.1 s image was 8.63e-09 erg cm^-2 s^-1 (0.2-10
keV).

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 101 seconds after the BAT trigger. There is a candidate afterglow in
the rapidly available 2.7'x2.7' sub-image at
  RA(J2000)  =	00:25:34.59 =	6.39413
  DEC(J2000) = -44:14:01.1  = -44.23364
with a 90%-confidence error radius of about 0.75 arc sec. This position is 9.7
arc sec. from the center of the XRT error circle. The estimated magnitude is
17.28 with a 1-sigma error of about  0.14. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.008.

Burst Advocate for this burst is M. J. Moss (mikejmoss3 AT gmail.com).
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/)