NOTE: uvot_fluxes_wget.pl vrs. 2024-08-27 fem at 250821d22h27m43s553800usUT
NOTE: Source region spec. is: 358.43975 -28.65328 4"
NOTE: Used archived XRT position of 358.43975 -28.65328  4.00
NOTE: position reference is GCN_Circulars-41472

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

GRB 250821A: Swift/UVOT Upper Limits

***UBS*** (***INSTITUTION***) and S. Dichiara (PSU)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 250821A
147 s after the BAT trigger (Dichiara et al., GCN Circ. 41462).
No optical afterglow consistent with the XRT position
*** POSITION REFERENCE is GCN_Circulars-41472 ***
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           147          297          147         >20.7
white              147         1716          428         >21.1
v                  381         1766          156         >18.9
b                  480         1682          127         >20.2
u                  455         1667          136         >19.7
w1                 430         5417          165         >20.4
w2                1375         1395           19         >19.3

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.015 in the direction of the burst
(Schlegel et al. 1998).