TITLE:   GCN CIRCULAR
NUMBER:  23784
SUBJECT: GRB 190123A: Swift/UVOT Upper Limits
DATE:    19/01/24 14:44:09 GMT
FROM:    Mike Siegel at PSU/Swift MOC  <mhs18@psu.edu>

M. H. Siegel (PSU) and A. D'Ai (INAF-IASFPA)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 190123A
124 s after the BAT trigger (D'Ai et al., GCN Circ. 23769).
No optical afterglow consistent with the XRT position
(Beardmore et al. GCN Circ. 23771)
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           124          250          123         >20.3
white              124        10248         1258         >22.0
v                 3470        11721          947         >20.3
b                 4290         5926          393         >21.1
u                 4085         5721          393         >21.0
w1                3880         5516          393         >20.1
m2                3675         5310          393         >19.9
w2                4701        11151         1079         >21.1

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.44 in the direction of the burst
(Schlegel et al. 1998).