{
  "submitter": "Owen Littlejohns at Az State U  <olittlej@asu.edu>",
  "editedOn": 1731005209808,
  "format": "text/plain",
  "circularId": 17736,
  "createdOn": 1429811229000,
  "version": 2,
  "bibcode": "2015GCN.17736....1L",
  "editedBy": "Leo P. Singer at NASA/GSFC <leo.p.singer@nasa.gov> on behalf of Leo P. Singer at NASA/GSFC <leo.p.singer@nasa.gov>",
  "eventId": "GRB 150423A",
  "body": "Owen Littlejohns (ASU), Nat Butler (ASU), Alan M. Watson (UNAM),\nAlexander Kutyrev (GSFC), William H. Lee (UNAM), Michael G. Richer\n(UNAM), Chris Klein (UCB), Ori Fox (UCB), J. Xavier Prochaska (UCSC),\nJosh Bloom (UCB), Antonino Cucchiara (ORAU/GSFC), Eleonora Troja\n(GSFC), Enrico Ramirez-Ruiz (UCSC), José A. de Diego (UNAM), Leonid\nGeorgiev (UNAM), Jesús González (UNAM), Carlos Román-Zúñiga (UNAM),\nNeil Gehrels (GSFC), and Harvey Moseley (GSFC) report:\n\nWe observed the field of GRB 150423A (Pagani, et al., GCN 17728) with\nthe Reionization and Transients Infrared Camera (RATIR; www.ratir.org)\non the 1.5m Harold Johnson Telescope at the Observatorio Astronómico\n\nNacional on Sierra San Pedro Mártir from 2015/04 23.41 to 2015/04\n23.48 UTC (3.30 to 5.01 hours after the BAT trigger), obtaining a\ntotal of 1.42 hours exposure in the r, i and z bands.\n\nFor a source within the Swift-XRT error circle (Evans, et al., GCN\n17735), in comparison with the SDSS DR9, we obtain the following\ndetections and upper limits (3-sigma):\n\n  r     23.77 +/- 0.23\n  i     23.62 +/- 0.26\n  z     > 20.33\n\nThese magnitudes are in the AB system and are not corrected for\nGalactic extinction in the direction of the GRB. Of the two sources\nreported by GROND (Varela, et al., GCN 17732), this source is at the\nposition of source 1. Our observations show a fading of 0.8 magnitudes\nin the i band, implying a power-law decay with a temporal index,\nt^-0.5. Similarly to the Keck observations (Perley, GCN 17733), we\nalso find source 2 reported by GROND to have remained at approximately\nconstant brightness.\n\nContinued observations are planned.\n\nWe thank the staff of the Observatorio Astronómico Nacional in San Pedro\nMártir.",
  "subject": "GRB 150423A: RATIR optical afterglow monitoring",
  "email": "olittlej@asu.edu"
}