NOTE: uvot_fluxes_wget.pl vrs. 2018-01-16 fem at 180821d22h41m29s284883usUT
NOTE: Source region spec. is: 7.7883 -38.6266 4"
NOTE: Used archived XRT position of   7.78830 -38.62660  4.00
NOTE: position reference is GCN_Notice

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

GRB 180821A: Swift/UVOT Upper Limits

F. E. Marshall (NASA/GSFC) and A. Tohuvavohu (PSU)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 180821A
219 s after the BAT trigger (Tohuvavohu et al., GCN Circ. 23158).
No optical afterglow consistent with the XRT position
*** POSITION REFERENCE is GCN_Notice ***
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           219          369          147         >20.6
white              219          495          167         >20.6
v                  526          546           19         >17.7
b                  451          471           19         >19.3
u                  426          446           19         >18.1
w1                 402          421           19         >19.2

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.02 in the direction of the burst
(Schlegel et al. 1998).