TITLE: GCN CIRCULAR NUMBER: 14409 SUBJECT: GRB 130420A: RATIR Optical and NIR Observations DATE: 13/04/20 11:56:25 GMT FROM: Alan M. Watson at Instituto de Astronomia UNAM Alan M. Watson (UNAM), Nat Butler (ASU), Alexander Kutyrev (GSFC), William H. Lee (UNAM), Michael G. Richer (UNAM), Chris Klein (UCB), Ori Fox (UCB) J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (UCSC), Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC), José A. de Diego (UNAM), Leonid Georgiev (UNAM), Jesús González (UNAM), Carlos Román-Zúñiga (UNAM), Neil Gehrels (GSFC), and Harvey Moseley (GSFC) report: We observed the field of GRB 130420A (Page, et al., GCN 14406) with the Reionization and Transients Infrared Camera (RATIR; www.ratir.org) on the 1.5m Harold Johnson Telescope at the Observatorio Astronómico Nacional on Sierra San Pedro Mártir from 2013/04 20.41 to 2013/04 20.45 UTC (2.48 to 3.38 hours after the BAT trigger), obtaining a total of 0.36 hours exposure in the r' and i' bands and 0.14 hours exposure in the Z, Y, J, and H bands. For a source within the Swift-XRT error circle, in comparison with SDSS DR8 and 2MASS, we find: r' 19.81 +/- 0.02 i' 19.41 +/- 0.02 Z 19.37 +/- 0.06 Y 18.99 +/- 0.07 J 19.16 +/- 0.07 H 18.87 +/- 0.11 These magnitudes are in the AB system and not corrected for Galactic extinction in the direction of the GRB. Uncertainties are 1-sigma. Comparison to the earlier photometry of Morgan et al. (GCN 14408) shows that this source has faded by about 2.5 magnitudes in J and H. We thank the staff of the Observatorio Astronómico Nacional in San Pedro Mártir. -- Dr. Alan M. Watson Instituto de Astronomía Universidad Nacional Autónoma de México