GCN Circular 28793

A. A. Breeveld (UCL-MSSL) and S. B. Cenko (GSFC) report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 201026A 88 s after the BAT trigger 
(Cenko et al., GCN Circ. 28784
Not found
 
 
).
No optical afterglow consistent with the XRT position (Goad et al., GCN Circ. 28791
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            88          238          147         >20.6
white               88          904          210         >20.9
u_FC               300          550          246         >20.1
v                  630          823           39         >18.3
b                  563          749           32         >19.2
u                  300          724          265         >20.2
w1                 680          873           39         >18.5
w2                4139         4518          197         >19.3

The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of 
E(B-V) = 0.18 in the direction of the burst (Schlegel et al. 1998).