TITLE:   GCN CIRCULAR
NUMBER:  27730
SUBJECT: GRB 200512A: Swift/UVOT Upper Limits
DATE:    20/05/13 16:56:49 GMT
FROM:    Frank Marshall at Swift/UVOT  <marshall@milkyway.gsfc.nasa.gov>

F. E. Marshall (NASA/GSFC) and K. K. Simpson (PSU)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 200512A
78 s after the BAT trigger (Simpson et al., GCN Circ. 27726).
No optical afterglow consistent with the enhanced XRT position
(Goad et al., GCN Circ. 27728) 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            78          228          147         >19.9
u_FC               236          486          246         >19.8
v                  567          760           39         >17.1
b                  493          858           58         >19.0
u                  236          833          285         >19.7
w1                 617          809           39         >17.9

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.03 in the direction of the burst
(Schlegel et al. 1998).