NOTE: uvot_fluxes_wget.pl vrs. 2024-08-27 fem at 250520d18h37m53s362288usUT
NOTE: Source region spec. is: 282.28575 -11.86914 4"
NOTE: Used archived XRT position of 282.28575 -11.86914  4.00
NOTE: position reference is GCN_Circulars-40494

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

GRB 250520A: Swift/UVOT Upper Limits

***UBS*** (***INSTITUTION***) and Eyles-Ferris (U. Leicester)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 250520A
126 s after the BAT trigger (Eyles-Ferris et al., GCN Circ. 40491).
No optical afterglow consistent with the XRT position
*** POSITION REFERENCE is GCN_Circulars-40494 ***
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           149          298          147         >20.3
white              149         1373          392         >20.4
v                  126         1251          110         >18.8
b                  481         1349           97         >19.8
u                  456         1324           97         >19.6
w1                 432         1300           97         >19.6
m2                 579         1275           78         >20.6
w2                 358         1394          112         >19.9

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.754 in the direction of the burst
(Schlegel et al. 1998).