NOTE: uvot_fluxes_wget.pl vrs. 2020-11-03a fem at 210918d15h14m20s162109usUT
NOTE: Source region spec. is: 250.4669 -45.5421 4"
NOTE: Used archived XRT position of 250.46690 -45.54210  4.00
NOTE: position reference is GCN_Notice

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

GRB 210918: Swift/UVOT Upper Limits

M. A. Baer (PSU) and ***BA*** (***BA INSTITUTION***)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 210918
134 s after the BAT trigger (***Author*** et al., GCN Circ. ????).
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

u_FC               134          384          246         >20.0
v                  440         4807          251         >19.3
b                  390         4396          274         >19.4
u                  134          920          356         >20.2
w1                 490         5133          172         >19.6
m2                 765         5012          216         >19.9
w2                 416         4602          255         >19.8

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 9.498 in the direction of the burst
(Schlegel et al. 1998).