NOTE: uvot_fluxes_wget.pl vrs. 2018-11-07 fem at 200228d17h53m10s779655usUT
NOTE: Source region spec. is: 252.04640 16.98523 4"
NOTE: Used archived XRT position of 252.04640  16.98523  4.00
NOTE: position reference is GCN_Circ-27256

=========== Draft Upper Limit Circular ========

GRB 200228B: Swift/UVOT Upper Limits

N. P. M. Kuin (UCL-MSSL) and S. L. Laha (GSFC/UMBC/CRESST)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 200228B
137 s after the BAT trigger (Laha et al., GCN Circ. 27254).
No optical afterglow consistent with the XRT position
*** POSITION REFERENCE is GCN_Circ-27256 ***
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

u_FC               137          387          246         >20.1
v                 4992        10685          676         >20.1
b                 4580         6012          393         >20.6
u                  137         5807          442         >20.4
w1                5402         5602          197         >19.5
m2                5197         5396          197         >19.8
w2                4786         6218          393         >19.4

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.092 in the direction of the burst
(Schlegel et al. 1998).