TITLE:   GCN CIRCULAR
NUMBER:  27840
SUBJECT: GRB 200528A: Swift/UVOT Upper Limits
DATE:    20/05/28 22:25:58 GMT
FROM:    Frank Marshall at Swift/UVOT  <marshall@milkyway.gsfc.nasa.gov>

F. E. Marshall (NASA/GSFC) and E. Ambrosi (INAF-IASFPA)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 200528A
81 s after the BAT trigger (Ambrosi et al., GCN Circ. 27832).
No optical afterglow consistent with the enhanced XRT position
(Evans et al. GCN Circ. 27836) 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            81          231          147         >21.1
u                  293          305           12         >18.7
v                 5743         5942          197         >18.8
b                 5127         5327          169         >20.7
uvw2              5538         5738          197         >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).