NOTE: uvot_fluxes_wget.pl vrs. 2024-08-27 fem at 250331d18h55m33s420304usUT
NOTE: Source region spec. is: 80.95621 33.06347 4"
NOTE: Used archived XRT position of  80.95621  33.06347  4.00
NOTE: position reference is GCN_Circulars-39977

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

GRB 250331C: Swift/UVOT Upper Limits

***UBS*** (***INSTITUTION***) and S. B. Cenko (GSFC)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 250331C
140 s after the BAT trigger (Cenko et al., GCN Circ. 39959).
No optical afterglow consistent with the XRT position
*** POSITION REFERENCE is GCN_Circulars-39977 ***
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           140          289          147         >21.1
u_FC               297          547          246         >19.9
white              140         1717          411         >22.3
v                  628         1767          136         >19.1
b                  553         1863          133         >20.1
u                  297         1841          363         >20.1
w1                 676         1817          136         >19.1
m2                 652         1792          136         >19.8
w2                 603         1743          136         >20.0

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.921 in the direction of the burst
(Schlegel et al. 1998).