TITLE:   GCN CIRCULAR
NUMBER:  33774
SUBJECT: GRB 230510A: Swift/UVOT Observations
DATE:    23/05/11 22:28:10 GMT
FROM:    Alexander Belles at PSU <aub1461@psu.edu>

A. Belles (PSU) and R. A. J. Eyles-Ferris (U Leicester)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 230510A
72 s after the BAT trigger (Eyles-Ferris et al., GCN Circ. 33752).
A source consistent with the XRT position (Evans et al., GCN Circ. 33756)
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 first
finding chart (FC) exposure and subsequent exposures are:

Filter      T_start(s)    T_stop(s)       Exp(s)           Mag
wh_FC               72          222          150      18.90+/-0.10
u_FC               284          318           34      18.09+/-0.32
wh                4413         4613          200      19.33+/-0.11
v                 4824         5024          200      18.97+/-0.32
b                 4209         5690          241      19.31+/-0.17
u                 5439         5638          199      19.10+/-0.24
w1                5234         5434          200      19.30+/-0.34
m2                5029         5228          199            >19.21
w2                4619         4819          200            >19.45

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.144 in the direction of the burst
(Schlegel et al. 1998).