TITLE: GCN CIRCULAR NUMBER: 41661 SUBJECT: GRB 250901A: Swift/UVOT Upper Limit DATE: 25/09/02 18:56:52 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 250901A 2.6 ks after the SVOM/ECLAIRs trigger (Piron et al., GCN Circ. 41634). We do not detect any afterglow consistent with the XRT position (Osborne et al., GCN Circ. 41645) or optical position (Xin et al., GCN Circ. 41646; Malesani et al., GCN Circ. 41649). 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 u 2629 4244 1589 >21.01 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.023 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/41661. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...