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.