TITLE: GCN CIRCULAR NUMBER: 41450 SUBJECT: GRB 250814A: Swift/UVOT Upper Limits DATE: 25/08/20 15:20:29 GMT FROM: Mike Siegel at PSU/Swift MOC <mhs18@psu.edu> M. H. Siegel (PSU) and R. Caputo (GSFC) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 250814A 179 s after the BAT trigger (Caputo et al., GCN Circ. 41358). No optical afterglow consistent with the XRT position (Salvaggio et al., GCN Circ. 41379) 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 u_FC 179 429 246 >20.3 white 460 1537 264 >21.8 v 510 1412 97 >20.2 b 436 1511 117 >20.2 u 179 1486 343 >20.5 w1 560 1462 97 >19.5 m2 708 1263 58 >18.6 w2 486 1556 130 >20.0 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 1.066 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/41450. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...