TITLE: GCN CIRCULAR NUMBER: 17101 SUBJECT: GRB 141121A: Continued RATIR Optical Observations DATE: 14/11/26 16:47:33 GMT FROM: Alan M. Watson at Instituto de Astronomia UNAM Nat Butler (ASU), Alan M. Watson (UNAM), Alexander Kutyrev (GSFC), William H. Lee (UNAM), Michael G. Richer (UNAM), Chris Klein (UCB), Ori Fox (UCB), J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (ORAU/GSFC), Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC), Jos� A. de Diego (UNAM), Leonid Georgiev (UNAM), Jes�s Gonz�lez (UNAM), Carlos Rom�n-Z��iga (UNAM), Neil Gehrels (GSFC), and Harvey Moseley (GSFC) report: We observed the field of GRB 141121A (Lien et al., GCN 17075) with the Reionization and Transients Infrared Camera (RATIR; www.ratir.org) on the 1.5m Harold Johnson Telescope at the Observatorio Astron�mico Nacional on Sierra San Pedro M�rtir from 2014/11 26.31 to 2014/11 26.53 UTC (123.55 to 128.80 hours after the BAT trigger), obtaining a total of 4.04 hours exposure in the r, i and z bands. For a source within the Swift-XRT error circle, in comparison with the SDSS DR9, we obtain the following detections and upper limits (3-sigma): r = 21.27 +/- 0.04 i = 21.04 +/- 0.04 z > 21.04 These magnitudes are in the AB system and are not corrected for Galactic extinction in the direction of the GRB. The afterglow has faded by about 0.3 magnitudes in r and i compared to our observations at 102 hours (Watson et al., GCN 17100). This corresponds to a further steepening of the temporal power law from t^-0.9 between 78 and 102 hours (Watson et al., GCN 17100) to t^-1.3 between 102 and 126 hours. We thank the staff of the Observatorio Astron�mico Nacional in San Pedro M�rtir.