TITLE:   GCN CIRCULAR
NUMBER:  28281
SUBJECT: GRB 200819A: Swift/UVOT Upper Limits
DATE:    20/08/21 20:55:50 GMT
FROM:    Mike Siegel at PSU/Swift MOC  <mhs18@psu.edu>

M. H. Siegel (PSU) 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 200819A
89 s after the BAT trigger (Dichiara et al., GCN Circ. 28263).
No optical afterglow consistent with the XRT position
(Evans et al. GCN Circ. 28265)
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            89          239          147         >20.4
u_FC               301          551          246         >19.0
white               89          601          167         >20.3
b                  557          577           19         >17.7
u                  301          551          246         >19.0

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 1.59 in the direction of the burst
(Schlegel et al. 1998).