TITLE:   GCN CIRCULAR
NUMBER:  31498
SUBJECT: GRB 220118A: Swift/UVOT Detection
DATE:    22/01/19 17:27:54 GMT
FROM:    Alexander Belles at PSU/Swift  <aub1461@psu.edu>

A. Belles (PSU) and N. J. Klingler (GSFC/UMBC/CRESSTII)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 220118A
99 s after the BAT trigger (Klingler et al., GCN Circ. 31490).
A fading source consistent with the XRT position
(Goad et al., GCN Circ. 31495) is detected in the initial
UVOT exposures.

The preliminary UVOT position is:
    RA  (J2000) =  12:49:04.52 = 192.26885 (deg.)
    Dec (J2000) = +22:54:56.2  =  22.91562 (deg.)
with an estimated uncertainty of 0.44 arc sec. (radius, 90% confidence).

Preliminary detections using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early
exposures are:

Filter         T_start(s)   T_stop(s)      Exp(s)           Mag

wh                 119          268          145      17.73+/-0.07
wh               11382        11797          404            >20.26
u                  276          454          175      17.33+/-0.12
b                10470        11377          885            >20.56


The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.025 in the direction of the burst
(Schlegel et al. 1998).