NOTE: uvot_fluxes_wget.pl vrs. 2023-03-23 fem at 230420d20h52m48s314561usUT
NOTE: Source region spec. is: 161.04817 32.10769 4"
NOTE: Used archived XRT position of 161.04817  32.10769  4.00
NOTE: position reference is GCN_Circulars-33661

=========== Draft Upper Limit Circular ========

GRB 230420: Swift/UVOT Upper Limits

S. R. Oates (U.Birmingham) and ***BA*** (***BA INSTITUTION***)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 230420
100 s after the BAT trigger (***Author*** et al., GCN Circ. ????).
No optical afterglow consistent with the XRT position
*** POSITION REFERENCE is GCN_Circulars-33661 ***
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           100          249          147         >21.1
u_FC               258          508          246         >20.0
white              100         1190          353         >20.8
v                  590         4885          255         >19.2
b                  514         1165           58         >19.7
u                  258         1141          285         >20.1
w1                 814         5109           52         >18.8
w2                4481         4681          197         >19.6

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.017 in the direction of the burst
(Schlegel et al. 1998).