TITLE: GCN CIRCULAR NUMBER: 35457 SUBJECT: GRB 240101A: Swift/UVOT Upper Limits DATE: 24/01/02 12:10:21 GMT FROM: Paul Kuin at MSSL <npkuin@gmail.com> N. P. M. Kuin (UCL-MSSL) and S. B. Cenko (GSFC) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 240101A 168 s after the BAT trigger (Cenko et al., GCN Circ. 35448). No optical afterglow consistent with the BAT position 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 168 318 147 >20.4 white 168 1053 334 >20.8 v 656 4661 236 >18.7 b 582 773 39 >18.9 u 729 749 19 >18.3 w1 705 5071 236 >19.5 w2 804 824 19 >18.7 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.059 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/35457. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...