TITLE:   GCN CIRCULAR
NUMBER:  41904
SUBJECT: GRB 250920C: Swift detection of a burst
DATE:    25/09/20 15:39:55 GMT
FROM:    David Palmer at LANL <palmer@lanl.gov>

R. Gupta (NASA GSFC), S. Dichiara (PSU), C. Gronwall (PSU),
J. A. Kennea (PSU), N. P. M. Kuin (UCL-MSSL), K. L. Page (U Leicester)
and D. M. Palmer (LANL) report on behalf of the Neil Gehrels Swift
Observatory Team:

At 15:25:17 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 250920C (trigger=1351039).  Swift slewed immediately to the burst.
The BAT on-board calculated location is 
RA, Dec 51.459, -29.646 which is 
   RA(J2000) = 03h 25m 50s
   Dec(J2000) = -29d 38' 44"
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 ~8500 counts/sec (15-350 keV), at ~0 sec after the trigger.

The XRT began observing the field at 15:27:21.2 UT, 123.8 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 51.4644, -29.6566 which is equivalent to:
   RA(J2000)  = 03h 25m 51.46s
   Dec(J2000) = -29d 39' 23.8"
with an uncertainty of 5.3 arcseconds (radius, 90% containment). This
location is 41 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 1.50e-09 erg cm^-2 s^-1 (0.2-10
keV).

There are no UVOT data available at this time.

Burst Advocate for this burst is R. Gupta (rahulbhu.c157 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/)