TITLE: GCN CIRCULAR NUMBER: 15192 SUBJECT: GRB 130907A: RATIR Optical and NIR Afterglow Confirmation DATE: 13/09/08 05:11:53 GMT FROM: Alan M. Watson at Instituto de Astronomia UNAM William H. Lee (UNAM), Nat Butler (ASU), Alan M. Watson (UNAM), Alexander Kutyrev (GSFC), 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 130907A (Page et al., GCN 15183) 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 2013/09 8.14 to 2013/09 8.15 UTC (5.57 to 6.03 hours after the BAT trigger), obtaining a total of 0.36 hours exposure in the r and i bands and 0.15 hours exposure in the Z, Y, J, and H bands. We detect a source at 14:23:34.01 +45:36:27.0 J2000 (+/- 0.5") with r = 20.01 +/- 0.03 i = 19.30 +/- 0.02 Z = 18.78 +/- 0.05 Y = 18.48 +/- 0.06 J = 18.13 +/- 0.06 H = 17.63 +/- 0.05 These magnitudes are in the AB system and are not corrected for Galactic extinction in the direction of the GRB. This source is outside the Swift-XRT error circle, but is only 0.8 arcsec from the transient source reported by de Ugarte Postigo et al. (GCN 15187) and 0.2 arcsec from the transient source reported by Trotter et al. (GCN 15191). From the close positional coincidence and fading magnitudes (r of 16.7, 19.6, and 20.0), we conclude all three observations are of the optical transient. The transient source is 0.5 arcsec from the faint galaxy SDSS J142333.95+453626.2, but is 1-2 magnitudes brighter in riZ. We thank the staff of the Observatorio Astronómico Nacional in San Pedro Mártir.