TITLE: GCN CIRCULAR NUMBER: 29311 SUBJECT: GRB 201221D: near-infrared observation with LBT DATE: 21/01/17 15:18:45 GMT FROM: Andrea Rossi at INAF A. Rossi (INAF-OAS) reports on behalf of the CIBO collaboration: We observed the location of the optical afterglow (Malesani et al., GCN 29117) of the short GRB 201221D (Page et al., GCN 29112) simultaneously in the J and Ks bands with the LUCI near-infrared imager and spectrograph mounted on the Large Binocular Telescope (LBT, Mt Graham, AZ, USA). Observations were obtained on 2020-12-24 at the UT midtime 11:40:00, i.e. ~2.5 days after the burst trigger, for a total of 20 min of exposure in each band. Inspection of the combined J and K-band images reveals a faint, extended source in both filters, for which we preliminary measure J=21.7+-0.3 (Vega system), calibrated against 2MASS field stars. We acknowledge the excellent support from the LBTO and LBT-INAF staff, particularly A. Cardwell, F. Cusano, and D. Paris, in obtaining these observations.