TITLE:   GCN CIRCULAR
NUMBER:  31351
SUBJECT: GRB 220101: Swift/UVOT Detection
DATE:    22/01/01 14:09:07 GMT
FROM:    Paul Kuin at MSSL  <npkuin@gmail.com>

N. P. M. Kuin (UCL-MSSL) and A. Tohuvavohu (U Toronto)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 220101
90 s after the BAT trigger ( Tohuvavohu et al., GCN Circ. 31347).
A rapidly decayig source consistent with the XRT position
(Osborne et al., GCN Circ. 31349) is detected in the initial UVOT exposures.

The preliminary UVOT position is:
    RA  (J2000) =  00:05:24.80 =   1.35334 (deg.)
    Dec (J2000) = +31:46:08.4  =  31.76899 (deg.)
with an estimated uncertainty of 0.42 arc sec. (radius, 90% confidence).

Preliminary detections and 3-sigma upper limits 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

white               90          240          147         14.68 +/- 0.02
v                 4448         4647          197         18.70 +/- 0.18
b                 3833         4032          197        >19.8
u                 3628         5201          334        >20.1
w1                4858         5057          197        >20.1
m2                4652         4852          197        >20.2
w2                4243         4443          197        >20.4

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.056 in the direction of the burst
(Schlegel et al. 1998).