GCN Circular 29898
Alan M. Watson (UNAM), Nat Butler (ASU), Rosa L. Becerra (UNAM), Simone Dichiara (GSFC/UMD), Alexander Kutyrev (GSFC/UMD), William H. Lee (UNAM), Oc��lotl Lopez (UNAM), Diego Gonzalez (UNAM), Margarita Pereyra (UNAM), Srihari Ravi (ASU), and Eleonora Troja (GSFC/UMD) report: We observed the field of the Fermi/GBM GRB 210424.694 (trigger 640975205) with the DDOTI wide-field imager at the Observatorio Astron��mico Nacional on Sierra San Pedro Martir (http://ddoti.astroscu.unam.mx) from 2021-04-25 03:39 to 11:50 UTC (from 11.0 to 19.2 hours after the trigger). We observed a region covering aproximately 20 degrees in RA and 20 degrees in declination (6 instrumental fields or about 400 square degrees) centered on the final GBM position and obtained 3420 to 3600 seconds of exposure per instrumental field in the w filter. We obtained AB photometry by calibration against the APASS catalog. We detect no likely candidate for the afterglow to our 10-sigma upper limits of w = 19.15 to 19.55 (interquartile range). We thank the staff of the Observatorio Astronomico Nacional in San Pedro Martir.