{
  "body": "Alan M. Watson (UNAM), Nat Butler (ASU), Alexander Kutyrev (GSFC), William \nH. Lee (UNAM), Michael G. Richer (UNAM), Chris Klein (UCB), Ori Fox (UCB), \nJ. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara \n(ORAU/GSFC), Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico \nRamirez-Ruiz (UCSC), José A. de Diego (UNAM), Leonid Georgiev (UNAM), \nJesús González (UNAM), Carlos Román-Zúñiga (UNAM), Neil Gehrels (GSFC), \nand Harvey Moseley (GSFC) report:\n\nWe observed the field of GRB 150728A (Krimm et al., GCN 18087) with the \nReionization and Transients Infrared Camera (RATIR; www.ratir.org) on the \n1.5m Harold Johnson Telescope at the Observatorio Astronómico Nacional on \nSierra San Pedro Mártir from 2015/07 31.22 to 2015/07 31.46 UTC (64.53 to \n70.24 hours after the BAT trigger), obtaining a total of 3.60 hours \nexposure in the r, i, and z bands.\n\nFor source A of Watson et al. (GCN 18096), we determine:\n\n   r 21.26 ± 0.04\n   i 20.90 ± 0.04\n   z 19.43 ± 0.13\n\nFor source B of Watson et al. (GCN 18096), we determine:\n\n   r 20.91 ± 0.04\n   i 20.70 ± 0.04\n   z 20.48 ± 0.31\n\nThese magnitudes are in comparison with the USNO-B1 and 2MASS catalogs, \nare in the AB system, and are not corrected for Galactic extinction in the \ndirection of the GRB.\n\nOur source A appears to correspond to the source reported by Dichiara et \nal. (GCN 18090). If this association is correct, then there is little \nevidence for fading between observations at about 1 hour, 16-23 hours, and \n65-70 hours. This is in contrast to the suggestion of Mazaeva et al. (GCN \n18097), who suggested that source A might indeed be the fading afterglow \non the basis of a 3-sigma non-detection at 30 hours.\n\nSimilarly, there is little evidence for fading of source B between 16-23 \nhours and 65-70 hours.\n\nWe thank the staff of the Observatorio Astronómico Nacional in San Pedro \nMártir.",
  "version": 2,
  "submitter": "Alan M. Watson at Instituto de Astronomia UNAM  <alan@astro.unam.mx>",
  "eventId": "GRB 150728A",
  "editedBy": "Vidushi Sharma at NASA GSFC/UMBC <vidushi.sharma@nasa.gov> on behalf of Leo P. Singer at NASA/GSFC <leo.p.singer@nasa.gov>",
  "editedOn": 1731008840978,
  "bibcode": "2015GCN.18098....1W",
  "createdOn": 1438365171000,
  "subject": "GRB 150728A: Continued RATIR Optical Observations",
  "format": "text/plain",
  "circularId": 18098,
  "email": "alan@astro.unam.mx"
}