NOTE: uvot_fluxes_wget.pl vrs. 2018-01-16 fem at 180426d11h05m11s969610usUT
NOTE: Source region spec. is: 245.197 -15.593 3"
NOTE: Used archived BAT position of 245.19700 -15.59300
NOTE: position reference is GCN_Position_Notice

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

GRB 180426: Swift/UVOT Upper Limits

A. A. Breeveld (UCL-MSSL) and ***BA*** (***BA INSTITUTION***)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 180426
145 s after the BAT trigger (***Author*** et al., GCN Circ. ????).
No optical afterglow consistent with the BAT position
*** POSITION REFERENCE is GCN_Position_Notice ***
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 initial exposures are:

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

v                  145          159           13         >17.6

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.36 in the direction of the burst
(Schlegel et al. 1998).