TITLE: GCN CIRCULAR NUMBER: 35477 SUBJECT: GRB 231220A: Swift-UVOT upper limit DATE: 24/01/04 03:26:25 GMT FROM: noelklin@umbc.edu N. Klingler (UMBC/NASA-GSFC/CRESST II) reports on behalf of the Swift-UVOT team: Swift-UVOT has performed follow-up observations of the Swift-BAT/GUANO-detected and Fermi-GBM-detected GRB 231220A, collecting 2.6 ks of data between T0+35.2 ks and T0+47.8 ks. No candidate counterpart was detected. The 3 sigma limiting (AB) magnitude in the White filter near the center of the BAT/GUANO localization (GCN 35409) is >23.20. View this GCN Circular online at https://gcn.nasa.gov/circulars/35477. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...