{
  "bibcode": "2021GCN.29898....1W",
  "body": "Alan M. Watson (UNAM), Nat Butler (ASU), Rosa L. Becerra (UNAM), Simone Dichiara\n(GSFC/UMD), Alexander Kutyrev (GSFC/UMD), William H. Lee (UNAM), Oc��lotl Lopez\n(UNAM), Diego Gonzalez (UNAM), Margarita Pereyra (UNAM), Srihari Ravi (ASU), and\nEleonora Troja (GSFC/UMD) report:\n\nWe observed the field of the Fermi/GBM GRB 210424.694 (trigger 640975205) with\nthe DDOTI wide-field imager at the Observatorio Astron��mico Nacional on Sierra\nSan Pedro Martir (http://ddoti.astroscu.unam.mx) from 2021-04-25 03:39 to 11:50\nUTC (from 11.0 to 19.2 hours after the trigger). \n\nWe observed a region covering aproximately 20 degrees in RA and 20 degrees in\ndeclination (6 instrumental fields or about 400 square degrees) centered on the\nfinal GBM position and obtained 3420 to 3600 seconds of exposure per\ninstrumental field in the w filter. We obtained AB photometry by calibration\nagainst the APASS catalog.\n\nWe detect no likely candidate for the afterglow to our 10-sigma upper limits of\nw = 19.15 to 19.55 (interquartile range).\n\nWe thank the staff of the Observatorio Astronomico Nacional in San Pedro Martir.",
  "circularId": 29898,
  "createdOn": 1619361988000,
  "email": "alan@astro.unam.mx",
  "eventId": "GRB 210424.694",
  "subject": "GRB 210424.694: DDOTI Upper Limits on the Afterglow",
  "submitter": "Alan M Watson at UNAM  <alan@astro.unam.mx>"
}