TITLE: GCN CIRCULAR NUMBER: 38422 SUBJECT: GRB 241128A: Swift/UVOT Upper Limits DATE: 24/12/02 19:11:35 GMT FROM: Sam Shilling at Lancaster University shilling.sam@gmail.com

S.P.R. Shilling (Lancaster U.) and Brivio (INAF-OAB) report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 241128A 3880 s after the BAT trigger (Brivio et al., GCN Circ. 38367). No optical afterglow consistent with the enhanced XRT position (Beardmore et al., GCN Circ. 38374) 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_FC 3880 4029 147 >20.0 white 3880 4649 344 >20.6 v 4860 5059 197 >19.0 b 4244 4444 197 >19.7 u 4038 4238 197 >19.2 m2 5065 10054 534 >19.4 w2 4655 4855 197 >19.3

The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.067 in the direction of the burst (Schlegel et al. 1998).

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