GRB 210321A: DDOTI Afterglow Confirmation

We observed the field of the Swift/BAT GRB 210321A (Dichiara et al., GCN Circ. 29677) with the DDOTI wide-field imager at the Observatorio Astronómico Nacional on Sierra San Pedro Martir ( http://ddoti.astroscu.unam.mx) starting at 2021-03-21 08:56 UTC (from 1.7 hours after the trigger). We observed a region covering approximately 7 degrees in RA and 10 degrees in declination (about 70 square degrees) centered on the XRT position (Perri et al., GCN 29678) in the w filter. Compared to the USNO-B1, Pan-STARRS DR1, and APASS DR10 catalogs, we detect a bright source at 08:39:50.04 +60:12:18.9 (J2000) fading from about w = 18. This confirms the afterglow reported in UVOT observations by Siegel et al. (GCN Circ. 29679). We thank the staff of the Observatorio Astronomico Nacional in San Pedro Martir.