GCN Circular 37147

N. P. M. Kuin (UCL-MSSL) and K. L. Page (U. Leicester)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB
240811A 102 s after the BAT trigger (Page et al., GCN Circ. 37136
Not found
 
 
).
No optical afterglow consistent with the XRT position (Beardmore
et al. GCN Circ. 37141
Not found
 
 
) 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           102          252          147         >21.0
u_FC               315          564          246         >20.7
white              102         1191          353         >21.9
v                  644         5026          255         >18.7
b                  570         1167           58         >20.0
u                  315         1142          285         >20.7
w1                1098         5251           34         >19.2
m2                5031         5231          197         >18.8
w2                4622         4821          197         >19.6

The magnitudes in the table are not corrected for the Galactic
extinction due to the reddening of E(B-V) = 0.023 in the direction
of the burst (Schlegel et al. 1998).