{
  "bibcode": "2019GCN.23820....1B",
  "body": "Nat Butler (ASU), Alan M. Watson (UNAM), Rosa L. Becerra (UNAM), Diego\nGonz��lez (UNAM), William H. Lee (UNAM), Margarita Pereyra (UNAM),\nAlexander Kutyrev (GSFC), Eleonora Troja (GSFC), and Tanner Wolfram (ASU)\nreport:\n\nWe observed the entire IPN error box of GRB 190129B (Hurley et al., GCN\nCirc. 23808) with the DDOTI/OAN wide-field imager at the Observatorio\nAstron��mico Nacional on Sierra San Pedro M��rtir\n(http://ddoti.astroscu.unam.mx) from 2019-01-30 02:15 UTC to 12:48 UTC\n(14.0 to 24.5 hours after burst) obtaining a total of 4.4 hours exposure\nin the w filter.\n\nIf we split our exposures roughly in two, in the first half from 02:15\nto 05:40 UTC we clearly detect a faint source close to the error region\nfor the candidate XRT afterglow (LaPorte et al., GCN Circ. 23813) at\n\n  07:49:50.82 +00:56:06.1 J2000 (+/- 0.5 arcsec). \n\nIn the second half from 05:41 to 12:48 UTC, this source is not visible.\n\nThe presence of a nearby bright star complicates photometry. However, in\nthe difference image we measure a magnitude and 1-sigma error of\n\n  w = 22.7 +/- 1.0.\n\nOur w magnitudes are calibrated against the USNO-B1 catalog (adjusted to\nan approximate AB system) and are not corrected for Galactic extinction\nin the direction of the GRB.\n\nWe assume this source corresponds to the sources reported previously by\nBolmer & Steinle (GCN Circ. 23814) and Piranomonte et al. (GCN Circ.\n23818) at a similar position and magnitude. However, our observations\nare the first to suggest fading, albeit at low significance.\n\nWe thank the DDOTI technical team and the staff of the Observatorio\nAstron��mico Nacional.",
  "circularId": 23820,
  "createdOn": 1548880344000,
  "email": "alan@astro.unam.mx",
  "subject": "GRB 190129B: DDOTI Detection of the Possible Afterglow and Suggestion of Fading",
  "submitter": "Alan M. Watson at Instituto de Astronomia UNAM  <alan@astro.unam.mx>",
  "eventId": "GRB 190129B"
}