TITLE:   GCN CIRCULAR
NUMBER:  31664
SUBJECT: GRB 220302A: Swift afterglow detection
DATE:    22/03/02 17:03:47 GMT
FROM:    Kim Page at U.of Leicester  <kimlpage1978@gmail.com>

E. Troja (NASA/GSFC/UMCP), C. Gronwall (PSU), J. A. Kennea (PSU),
K. L. Page (U Leicester), D. M. Palmer (LANL),
T. M. Parsotan (GSFC/UMBC/CRESSTII) and A. Tohuvavohu (U Toronto)
report on behalf of the Neil Gehrels Swift Observatory Team:

Continuing the recovery from the Reaction Wheel anomaly, Swift has performed a
follow-up observation of GRB 220302A which occurred at 07:40:19 UT (Troja et al., 
GCN 31661). 

The XRT began observing the field at 16:41:18.7 UT, 32459.3 seconds
after the BAT trigger. Using promptly downlinked data we find an
uncatalogued X-ray source located at RA, Dec 301.43151, 49.38868 which
is equivalent to:
   RA(J2000)  = 20h 05m 43.56s
   Dec(J2000) = +49d 23' 19.2"
with an uncertainty of 4.7 arcseconds (radius, 90% containment). This
location is 1.6 arcseconds from the BAT onboard position, within the
BAT error circle. This position may be improved as more data are
received; the latest position is available at
https://www.swift.ac.uk/sper.  We cannot determine whether the source
is fading at the present time. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density consistent with the Galactic value of 3.44
x 10^21 cm^-2 (Willingale et al. 2013). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 32463 seconds after the BAT trigger. No credible afterglow candidate
has been found in the initial data products. The 2.7'x2.7' sub-image covers
100% of the XRT error circle. The typical 3-sigma upper limit has been about
19.6 mag. The 8'x8' region for the list of sources generated on-board covers
100% of the XRT error circle. The list of sources is typically complete to
about 18 mag. No correction has been made for the expected extinction
corresponding to E(B-V) of 0.216. 

Burst Advocate for this burst is E. Troja (nora.gsfc 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/)