TITLE: GCN CIRCULAR NUMBER: 23189 SUBJECT: GRB 180828A: RATIR Optical and NIR Observations DATE: 18/08/29 16:14:03 GMT FROM: Nat Butler at Az State U Nat Butler (ASU), Alan M. Watson (UNAM), 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 180828A (Beardmore, et al., GCN 23182) 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 2018/08 29.14 to 2018/08 29.28 UTC (8.29 to 11.70 hours after the BAT trigger), obtaining a total of 1.73 hours exposure in the r and i bands and 0.79 hours exposure in the Z, Y, J, and H bands. We find one uncatalogued source within the Swift-XRT error circle (Beardmore at at., GCN 23182) at RA, Dec = 17:54:52.5 -25:47:56.3 (J2000, +/-0.5"). This source is outside the enhanced XRT error region (Evans et al., GCN 23184), within which we find no new sources. In comparison with the 2MASS catalog, we obtain the following detection and 3-sigma upper limit: J > 21.4 H = 20.8 +/- 0.3 These magnitudes are in the AB system and are not corrected for Galactic extinction in the direction of the GRB. We note that this field has high extinction, with E[B-V]~16. We thank the staff of the Observatorio Astronómico Nacional in San Pedro Mártir.