TITLE:   GCN CIRCULAR
NUMBER:  25544
SUBJECT: GRB 190828B: Swift/UVOT Upper Limits
DATE:    19/08/29 13:01:37 GMT
FROM:    Samantha Oates at MSSL  <sro@mssl.ucl.ac.uk>

S. R. Oates (U.Warwick) and S. Dichiara (NASA/GSFC/UMCP)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 190828B
63 s after the BAT trigger (Dichiara et al., GCN Circ. 25517).
No optical afterglow consistent with the XRT position
(Beardmore et al. GCN Circ. 25521)
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            63          213          147         >20.8
u_FC               275          525          246         >20.1
white               63         1717          411         >21.4
v                  605         1767          136         >19.1
b                  530         1693          117         >20.0
u                  275         1668          363         >20.4
w1                 654         1644          117         >19.2
m2                 630         5626          259         >19.4
w2                 580         1743          136         >19.3

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.10 in the direction of the burst
(Schlegel et al. 1998).