TITLE: GCN CIRCULAR NUMBER: 20911 SUBJECT: GRB 170317A: RATIR Optical and NIR Observations DATE: 17/03/18 17:10:21 GMT FROM: Nat Butler at UC berkeley Alan M. Watson (UNAM), 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 (UVI), Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC), Jesús González (UNAM), Carlos Román-Zúñiga (UNAM), Harvey Moseley (GSFC), John Capone (UMD), V. Zach Golkhou (ASU), and Vicki Toy (UMD) report: We observed the field of GRB 170317A (LaPorte et al., GCN 20885) 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 2017/03 18.13 to 2017/03 18.30 UTC (17.37 to 21.38 hours after the BAT trigger), obtaining a total of 2.84 hours exposure in the r and i bands and 1.19 hours exposure in the Z, Y, J, and H bands. For a source within the enhanced Swift-XRT error circle (Beardmore et al., GCN 20887), in comparison with the USNO-B1 and 2MASS catalogs, we obtain the following detections and 3-sigma upper limits: r 22.85 +/- 0.05 i 22.86 +/- 0.09 Z 22.92 +/- 0.30 Y 22.34 +/- 0.26 J 22.41 +/- 0.35 H > 21.95 These magnitudes are in the AB system and are not corrected for Galactic extinction in the direction of the GRB. We thank the staff of the Observatorio Astronómico Nacional in San Pedro Mártir.