TITLE: GCN CIRCULAR NUMBER: 19602 SUBJECT: GRB 160625B: RATIR Optical and NIR Observations DATE: 16/06/27 14:12:33 GMT FROM: Alan M. Watson at Instituto de Astronomia UNAM Alan M. Watson (UNAM), Eleonora Troja (GSFC), Nat Butler (ASU), Alexander Kutyrev (GSFC), William H. Lee (UNAM), Michael G. Richer (UNAM), Ori Fox (STScI), J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (GSFC/STScI), 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), Harvey Moseley (GSFC), John Capone (UMD), V. Zach Golkhou (ASU), and Vicki Toy (UMD) report: We observed the field of the Fermi LAT GRB 160625B (Dirirsa, et al., GCN 19580) 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 2016/06 27.36 to 2016/06 27.47 UTC (33.89 to 36.56 hours after the BAT trigger), obtaining a total of 1.73 hours exposure in the r and i bands and 0.73 hours exposure in the Z, Y, J, and H bands. We detect the afterglow reported by Troja et al. (GCN Circ. 19588) and, in comparison with the USNO-B1 and 2MASS catalogs, obtain the following magnitudes: r = 19.63 +/- 0.01 i = 19.52 +/- 0.01 Z = 19.34 +/- 0.02 Y = 19.17 +/- 0.02 J = 19.11 +/- 0.02 H = 18.98 +/- 0.03 These magnitudes are in the AB system and are not corrected for Galactic extinction in the direction of the GRB. The afterglow has faded by about 1.20 magnitude in all bands compared to our earlier epoch, confirming the fading seen during the first epoch. The fading is consistent with a temporal index of -0.90. More observations are planned. We thank the staff of the Observatorio Astronómico Nacional in San Pedro Mártir. [GCN OPS NOTE(27jun16): Per author's request, the GRB name in the Title was changed from "A" to "B". The name in the text was/is correct.]