TITLE:   GCN CIRCULAR
NUMBER:  12466
SUBJECT: GRB 111020A: Swift/UVOT Upper Limits
DATE:    11/10/20 19:47:57 GMT
FROM:    Samantha Oates at MSSL  <sro@mssl.ucl.ac.uk>

S. R. Oates (MSSL-UCL) and T. Sakamoto (NASA/UMBC)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 111020A
80 s after the BAT trigger (Sakamoto et al., GCN Circ. 12460).
No optical afterglow consistent with the XRT position (Osborne et al., GCN Circ. 12463) 
is detected in the initial UVOT exposures. 

Preliminary 3-sigma upper limits using the UVOT photometric system
(Poole et al. 2008, MNRAS, 383, 627) for the first finding chart (FC)
exposure and subsequent exposures are:

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

white_FC            80          230          147         >20.0
u_FC               292          542          246         >19.6
white               80         7160          766         >20.3
v                  622         6135          275         >18.8
b                  547         6956          471         >19.9
u                  292        18728         1973         >20.3
w1                 670        18066         2242         >21.0
m2                6140        22385         2310         >21.1
w2                1027         5930          216         >20.5

This photometry may be complicated by the presence of a catalogued source 
approximately 3'' away from the centre of the enhanced XRT error circle.
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.43 in the direction of the burst
(Schlegel et al. 1998).