{
  "bibcode": "2018GCN.23253....1W",
  "body": "Alan M. Watson (UNAM), Nat Butler (ASU), Eleonora Troja (GSFC), Rosa L.\nBecerra (UNAM), William H. Lee (UNAM), and Alexander Kutyrev (GSFC)\nreport:\n\nWe observed the field of GRB 180914B (Ursi et al., GCN Circ. 23226) with\nthe DDOTI/OAN wide-field imager at the Observatorio Astronomico\nNacional on Sierra San Pedro Martir (http://ddoti.astroscu.unam.mx) from\n2018-09-16 02:54 to 06:02 (32.5 to 35.7 hours after burst) and\n2018-09-17 02:58 to 04:17 (56.6 to 57.9 after burst) obtaining 7200 and\n3060 seconds exposure with no filter.\n\nWe detect the optical counterpart (Zheng & Filippenko, GCN Circ. 23237;\nTroja, et al., GCN Circ. 23238) with the following magnitudes:\n\nw = 19.45 +/- 0.10 (on 2018-09-16) \nw = 20.25 +/- 0.31 (on 2018-09-17)\n\nThese AB magnitudes are calibrated against the Pan-STARRS1 catalog and\nare not corrected for Galactic extinction in the direction of the GRB.\n\nWe confirm the fading reported by de Ugarte Postigo et al. (GCN Circ.\n23239), Troja et al. (GCN Circ. 23243), and Mazaeva et al. (GCN Circ.\n23249).\n\nDDOTI/OAN imaged the entire Fermi/LAT error region (Bissaldi et al., GCN\nCirc. 23232). We confirm that there were no other uncatalogued sources\nin the region on 2019-09-16 to a 10-sigma limit of w = 19.4.\n\nWe thank the staff of the Observatorio Astronomico Nacional in San Pedro\nMartir.",
  "circularId": 23253,
  "createdOn": 1537232128000,
  "email": "alan@astro.unam.mx",
  "subject": "GRB 180914B: DDOTI/OAN Detection and Confirmation of Fading",
  "submitter": "Alan M. Watson at Instituto de Astronomia UNAM  <alan@astro.unam.mx>",
  "eventId": "GRB 180914B"
}