TITLE:   GCN CIRCULAR
NUMBER:  28793
SUBJECT: GRB 201026A: Swift/UVOT Upper Limits
DATE:    20/10/27 14:17:32 GMT
FROM:    Alice Breeveld at MSSL-UCL  <a.breeveld@ucl.ac.uk>

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).
No optical afterglow consistent with the XRT position (Goad et al., GCN Circ. 28791) 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).