TITLE:   GCN CIRCULAR
NUMBER:  33739
SUBJECT: GRB 230506C: Swift/UVOT Upper Limits
DATE:    23/05/07 11:27:27 GMT
FROM:    Paul Kuin at MSSL <npkuin@gmail.com>

Paul Kuin (MSSL/UCL) and A Tohuvavohu (U Toronto) report on behalf
of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 230506C
4.6 ks after the BAT trigger (Tohuvavohu et al., GCN Circ. 33731).
No optical afterglow consistent with the enhanced XRT position 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             4625         4825          197         >18.5
v                 5036         5236          197         >19.2
u                 5614         5814          197         >19.6
uvw1              5446         5646          197         >20.6
uvm2              5241         5441          197         >21.5
uvw2              4831         5031          197         >20.3