TITLE: GCN CIRCULAR NUMBER: 14439 SUBJECT: GRB 130420A: Continued RATIR Optical and NIR Observations DATE: 13/04/22 21:22:43 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 again observed the field of GRB 130420A (Page et al., GCN Circular 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 22.35 to 2013/04 22.47 UTC (48.84 to 51.69 hours after the BAT trigger), obtaining a total of 0.71 hours exposure in the r' and i' bands and 0.29 hours exposure in the Z, Y, J, and H bands. The afterglow is again detected in several bands. In comparison with SDSS DR8 and 2MASS, we obtain: r' 22.63 +/- 0.17 i' 22.46 +/- 0.17 Z 21.62 +/- 0.25 Y > 21.32 J > 21.39 H > 20.91 These magnitudes are in the AB system, quoted with 1-sigma uncertainty, and not corrected for Galactic extinction in the direction of the GRB. The upper limits are at the 3-sigma level. In comparison with our earlier observations (Watson et al., GCN Circular 14409; Butler et al., GCN Circular 14431), we see that the afterglow faded by about 2 magnitudes from about 3 to about 25 hours after the Swift trigger, but then by only about another 0.5 magnitudes from about 25 to about 50 hours after the Swift trigger. We thank the staff of the Observatorio Astronómico Nacional in San Pedro Mártir.