GCN Circular 29144
Huang, K. (CYCU), Urata, Y. (NCU) and Petitpas, G (SAO). report: We observed the field of the GRB201221D (Page et al., GCN #29112) at 228 GHz using the Submillimeter Array (SMA). The observation was started at 2020 December 11:27 UT (12.3 h after the burst). There was no source at the candidate of optical afterglow (Malesani et al., GCN #29117; Dichiara et al., GCN #29128; de Ugarte Postigo et al., GCN #29132; Kilpatrick et al., GCN #29133; Rastinejad et al. GCN #29142). The preliminary limit of the observation is ~0.2 mJy (rms). We thank Ramprasad Rao, Mark Gurwell and staff of SMA for the scheduling and execution of observations.