TITLE: GCN CIRCULAR NUMBER: 22061 SUBJECT: GRB 171027A: RATIR Confirmation of Fading and Photo-z DATE: 17/10/27 14:50:03 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 continued to observe the field of GRB 171027A (D'Avanzo et al., et al., GCN 22053) 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 2017/10 27.35 to 2017/10 27.53 UTC (0.04 to 4.24 hours after the BAT trigger), obtaining a total of 2.82 hours exposure in the r and i bands and 1.18 hours exposure in the Z, Y, J, and H bands. At late time, the source is only detected in the H-band, with H = 19.12 +/- 0.06. This magnitude is calibrated relative to 2MASS and is in the AB system, not corrected for Galactic extinction in the direction of the GRB. We measure a fade in the H-band flux in time as t^(-1.0+/-0.1). Using all bands (see, Watson et al., GCN 22057), we find high A_V photo-z solutions nearby (z<3.85, 90% conf.) and a high-z solution which assumes A_V=0 (z=9+/-1). We note that the XRT N_H constraints (D'Avanzo et al., et al., GCN 22053) point toward the high A_V solution, although with low statistical significance. We thank the staff of the Observatorio Astronómico Nacional in San Pedro Mártir.