TITLE: GCN CIRCULAR NUMBER: 23396 SUBJECT: GRB 181030A: RATIR Optical and NIR Observations DATE: 18/10/30 15:56:06 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), 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 (U. Wash.), and Vicki Toy (UMD) report: We observed the field of GRB 181030A (Sonbas et al., GCN Circ. 23389) 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 2018/10 30.41 to 2018/10 30.53 UTC (8.40 to 11.29 hours after the BAT trigger), obtaining a total of 0.82 hours exposure in the r and i bands and 0.39 hours exposure in the Z, Y, J, and H bands. For a source within the XRT error circle, in comparison with the SDSS DR9 and 2MASS catalogs, we obtain the following upper limits (3-sigma): r > 22.25 i > 22.11 Z > 21.07 Y > 20.80 J > 20.31 H > 19.61 These magnitudes are in the AB system and are not corrected for Galactic extinction in the direction of the GRB. The afterglow has clearly faded since the early observations of Sonbas et al. (GCN Circ. 23389), Moskvitin & Spiridonova (GCN Circ. 23390), and Lipunov et al. (GCN Circ. 23392). We thank the staff of the Observatorio Astronómico Nacional in San Pedro Mártir.