GCN Circular 33471

A. A. Breeveld (UCL-MSSL), and C. Salvaggio (INAF-OAB) report on behalf 
of the Swift/UVOT team:

The Swift/UVOT began observations of the field of GRB 230307A 99.5 ks 
after the Fermi/GBM-detected trigger (Dalessi et al., GCN 33407
Not found
 
 
).
A fading source consistent with the enhanced XRT position (Burrows et 
al., GCN 33465
Not found
 
 
) and consistent with the optical counterpart reported by 
Levan et al. (GCN 33439
Not found
 
 
), Lipunov et al. (GCN 33441
Not found
 
 
), Fulton et al. (GCN 
33443
Not found
 
 
), O'Connor et al. (GCN 33447
Not found
 
 
), Im et al. (GCN 33449
Not found
 
 
), Vanderspek 
et al. (GCN 33453
Not found
 
 
) and Bom et al. (GCN 33459
Not found
 
 
) is detected in the initial 
UVOT exposures. Detections and 3 sigma upper limits are given in the 
following table:

Filter      T_start(s) T_stop(s)   Exp(s)   Mag

white        99525      110441      2265     21.28 +/- 0.16
white       133031      208070      2931     22.09 +/- 0.32
white       212899      420530      3418    >22.25
u            83621       88252       422    >20.44

The magnitudes in the table are not corrected for the Galactic 
extinction due to the reddening of E(B-V) = 0.084 in the direction of 
the burst (Schlegel et al. 1998).