TITLE: GCN CIRCULAR NUMBER: 22514 SUBJECT: GRB 180316A: RATIR Optical Observations, Possible Re-brightening DATE: 18/03/17 15:19:48 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 180316A (Melandri,, et al., GCN 22500) 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 2018/03 17.39 to 2018/03 17.52 UTC (28.35 to 31.55 hours after the BAT trigger), obtaining a total of 2.36 hours exposure in the r and i bands. The optical afterglow (e.g., Lipunov, et al., GCN 22502) is again cleanly detected. In comparison with the USNO-B1 catalog, we obtain: r = 20.23 +/- 0.02 i = 19.93 +/- 0.01 These magnitudes are in the AB system and are not corrected for Galactic extinction in the direction of the GRB. These magnitudes are comparable to those reported for RATIR for 2018/03.16 (Butler, et al., GCN 22509). During that observation, the afterglow was fading strongly. We again observe the afterglow to be fading, as t^(-0.7+/-0.3), and we infer that the afterglow may have brightened between our epochs, at a time around 1 day after the GRB. We thank the staff of the Observatorio Astronómico Nacional in San Pedro Mártir.