TITLE: GCN CIRCULAR NUMBER: 26001 SUBJECT: GRB 191011A: RATIR Optical and NIR Observations DATE: 19/10/11 15:41:42 GMT FROM: Alan M Watson at 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), Diego González (UNAM), 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 191011A (Laha et al., GCN Circ. 25988) 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 2019/10 11.26 to 2019/10 11.48 UTC (1.60 to 6.94 hours after the BAT trigger), obtaining a total of 1.64 hours exposure in the i band and 0.49 hours exposure in the Z, Y, J, and H bands. For a source within the Swift-XRT error circle, in comparison with the USNO-B1 and 2MASS catalogs, we obtain the following detections and upper limits (3-sigma): i = 21.59 +/- 0.13 Z = 21.22 +/- 0.21 Y > 21.76 J > 19.81 H > 20.54 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.