TITLE: GCN CIRCULAR NUMBER: 31855 SUBJECT: GRB 220408A: Swift/UVOT Detection DATE: 22/04/08 15:34:23 GMT FROM: Samantha Oates at MSSL S. R. Oates (U.Birmingham) and R. Caputo (GSFC) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 220408A 112 s after the BAT trigger (Caputo et al., GCN Circ. 31848). A source consistent with the XRT position (Beardmore et al., GCN Circ. 31852) is detected in the initial white UVOT exposure only. 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) 112 262 147 20.30 +/- 0.22 white 605 799 40 >21.4 v 655 675 19 >19.3 b 581 774 39 >20.7 u 325 575 246 >20.2 w1 704 724 19 >17.9 m2 679 699 19 >17.4 w2 631 650 19 >17.7 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.042 in the direction of the burst (Schlegel et al. 1998).