TITLE:   GCN CIRCULAR
NUMBER:  27539
SUBJECT: GRB 200411A: Swift/UVOT Upper Limits
DATE:    20/04/11 09:55:39 GMT
FROM:    Paul Kuin at MSSL  <npkuin@gmail.com>

N. P. M. Kuin (UCL-MSSL) and A. Tohuvavohu (U. Toronto)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 200411A
58 s after the BAT trigger (Tohuvavohu et al., GCN Circ. 27536). No optical
afterglow consistent with the XRT position (Osborne et al., GCN Circ.
27538) 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            58          208          147         >20.8
u_FC               270          520          246         >20.4
white               58         1540          392         >21.2
v                  601         1417           97         >18.5
b                  525         1343           78         >20.3
u                  270         1490          343         >21.0
w1                 651         1466           97         >18.8
m2                 626          646           19         >18.1
w2                 576         1220           58         >19.2

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.02 in the direction of the burst
(Schlegel et al. 1998).