{
  "subject": "GRB 150817A: Continued RATIR Optical Observations - Afterglow Confirmation",
  "circularId": 18156,
  "version": 2,
  "body": "Alan M. Watson (UNAM), Nat Butler (ASU), Alexander Kutyrev (GSFC), William \nH. Lee (UNAM), Michael G. Richer (UNAM), Ori Fox (UCB), J. Xavier \nProchaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (ORAU/GSFC), \nEleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC), \nJosé A. de Diego (UNAM), Leonid Georgiev (UNAM), Jesús González (UNAM), \nCarlos Román-Zúñiga (UNAM), Neil Gehrels (GSFC), Harvey Moseley (GSFC), \nJohn Capone (UMD), V. Zach Golkhou (ASU), and Vicki Toy (UMD) report:\n\nWe observed the field of GRB 150817A (D'Elia, et al., GCN 18143) 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 2015/08 18.16 to 2015/08 18.27 UTC (25.78 to \n28.42 hours after the BAT trigger), obtaining a total of 1.77 hours \nexposure in the r, i, and z bands.\n\nThe first source reported by Butler et al. (GCN 18144) has not faded since \nour first epoch of observations.\n\nThe second source, reported by Butler et al. (GCN 18145), has continued to \nfade and is now only marginally detected. In comparison with the USNO-B1 \nand 2MASS catalogs, we obtain the following marginal detections and upper \nlimit (3-sigma):\n\n   r = 23.8 ± 0.4\n   i = 23.8 ± 0.3\n   z > 20.2\n\nThese magnitudes are in the AB system and are not corrected for Galactic \nextinction in the direction of the GRB.\n\nWe note that the second source is consistent with the enhanced Swift-XRT \nerror circle (Osborne et al. GCN 18146). This coincidence and the clear \nfading suggest that it is the afterglow of the GRB.\n\nWe thank the staff of the Observatorio Astronómico Nacional in San Pedro \nMártir.",
  "bibcode": "2015GCN.18156....1W",
  "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>",
  "format": "text/plain",
  "eventId": "GRB 150817A",
  "submitter": "Alan M. Watson at Instituto de Astronomia UNAM  <alan@astro.unam.mx>",
  "email": "alan@astro.unam.mx",
  "createdOn": 1439915387000,
  "editedOn": 1731009623989
}