TITLE:   GCN CIRCULAR
NUMBER:  33733
SUBJECT: GRB 230506B: Swift/UVOT Detection
DATE:    23/05/06 21:37:07 GMT
FROM:    Paul Kuin at MSSL <npkuin@gmail.com>

Paul Kuin (MSSL/UCL) and Simone Dichiara(PSU) report on behalf
of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 230506B
114 s after the BAT trigger (Dichiara et al., GCN Circ. 33727).
A candidate afterglow consistent with the 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              113          271          147          20.19 +/- 0.24
white              614          807           38         >19.8
u                  334          583          247         >19.9
u                10511        11899          738          20.66 +/- 0.30
b                  589          783           39         >19.1
uvw1               714          734           20         >17.6
uvm2               688          708           20         >17.2
uvw2               639          658           20         >19.6

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.293 in the direction of the burst
(Schlegel et al. 1998).

[GCN OPS NOTE: Corrected title from 230606B to 230506B at author's request.]