TITLE:   GCN CIRCULAR
NUMBER:  35607
SUBJECT: GRB 240118A: Swift/UVOT Upper Limits
DATE:    24/01/23 17:35:39 GMT
FROM:    Mike Siegel at PSU/Swift MOC <mhs18@psu.edu>

M. H. Siegel (PSU) reports on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 240118A
96191 s after the LAT trigger (Bissaldi et al., GCN Circ. 35560). No optical afterglow consistent with the
LAT position or the XRT position (Beardmore et al., GCN Circ. 35587)  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 initial exposures are:

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

u                96191       103639         3161         >20.8

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.056 in the direction of the burst
(Schlegel et al. 1998).