GCN Circular 34399

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

The Swift/UVOT began settled observations of the field of GRB 230812
25418 s after the GBM trigger (Roberts et al., GCN Circ. 34391
Not found
 
 
).
The Fermi LAT also detected the trigger (Scotton et al, GCN Circ. 34392
Not found
 
 
).
An candidate optical counterpart was reported (Zheng & Filippenko, GCN
Circ.
34395
Not found
 
 
; Lipunov et al., GCN Circ 34396
Not found
 
 
; Salgundi et al., GCN Circ. 34397
Not found
 
 
)
near the reported XRT candidate (Kennea, GCN Circ. 34393
Not found
 
 
, Page, GCN Circ.
34394
Not found
 
 
).  A source consistent with the XRT position is detected in the UVOT
exposures.

Preliminary detections using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures
are:

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

white            25418        31151          390         20.48 +/- 0.18

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.024 in the direction of the burst
(Schlegel et al. 1998).