TITLE:   GCN CIRCULAR
NUMBER:  23684
SUBJECT: GRB 190103B: Swift/UVOT Upper Limits
DATE:    19/01/14 15:53:58 GMT
FROM:    Paul Kuin at MSSL  <npkuin@gmail.com>

A. A. Breeveld (UCL-MSSL) and A. Y. Lien (GSFC/UMBC) report on behalf of
the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 190103B
103 s after the BAT trigger (Lien et al., GCN Circ. 23602).
No optical afterglow consistent with the XRT position (Evans et al. GCN
Circ. 23603) is detected in the initial UVOT exposures.
Preliminary 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding
chart (FC) exposure and subsequent exposures are:

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

white_FC           103          253          147         >20.5
u_FC               316          565          246         >19.5
white              103        23827         1860         >21.8
v                  646        40393         2202         >20.6
b                  571        46547         2987         >21.5
u                  316        46101         3922         >21.3
w1                4776        45188         3715         >21.2
m2                4570        41036         2792         >21.1
w2                4161        39480         1904         >21.0

The magnitudes in the table are not corrected for the Galactic
extinction due to the reddening of E(B-V) = 0.01 in the direction of the
burst (Schlegel et al. 1998).