{
  "bibcode": "2021GCN.29858....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 Swift/BAT GRB 210420B (Moss et al., GCN Circ.\n29844) with the DDOTI wide-field imager at the Observatorio Astron��mico Nacional\non Sierra San Pedro Martir (http://ddoti.astroscu.unam.mx) from 2021-04-21 04:36\nto 08:15 UTC (from 10.0 to 13.7 hours after the trigger) and obtained 10380\nseconds of exposure in the w filter.\n\nWe observed a region covering aproximately 7 degrees in RA and 10 degrees in\ndeclination (about 70 square degrees), including the XRT position. We calibrated\nour images against the APASS catalog.\n\nWe detect a source at 16:57:17.97 +42:34:12.3 J2000 with an AB magnitude of w =\n21.47 +/- 0.09.\n\nThis source is outside the XRT error region reported by Moss et al. (GCN Circ.\n29844), but is not present in the Pan-STARRS DR1 g image of the field and is\nconsistent with the afterglow coordinates reported by Oksanen (GCN Circ. 29846),\nLipunov et al. (GCN Circ. 29845), Leonini et al. (GCN Circ. 29851), and de\nUgarte Postigo et al. (GCN Circ. 29852).\n\nWe thank the staff of the Observatorio Astronomico Nacional in San Pedro Martir.",
  "circularId": 29858,
  "createdOn": 1618996545000,
  "email": "alan@astro.unam.mx",
  "subject": "GRB 210420B: DDOTI Detection of the Afterglow",
  "submitter": "Alan M Watson at UNAM  <alan@astro.unam.mx>",
  "eventId": "GRB 210420B"
}