TITLE:   GCN CIRCULAR
NUMBER:  34135
SUBJECT: GRB 230628E: Swift/UVOT Detection
DATE:    23/07/02 18:36:09 GMT
FROM:    Samantha Oates at University of Birmingham <samantha.oates@alumni.ucl.ac.uk>

S. R. Oates (U. Birmingham) and N. Klingler (NASA-GSFC/UMBC/CRESST II)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 230628E
221 s after the BAT trigger (Klingler et al., GCN Circ. 34110).
A source consistent with the XRT position (Page et al., GCN Circ. 34116)
and the optical position (Malesani et al., GCN Circ. 34118)
is detected in the initial UVOT exposures.

Preliminary detections and 3-sigma upper limits 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 (FC)         221          371          167         20.10 +/- 0.20
wh                 501         1194          223         20.69 +/- 0.34       
v                  379         1243           68        >19.1
b                  477         1170           78        >19.9
u                  452         1145           78        >19.6
w1                 428         1120           78        >19.4
m2                1249         1269           19        >18.2
w2                 700          720           19        >18.5

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.040 in the direction of the burst
(Schlegel et al. 1998).