TITLE: GCN CIRCULAR NUMBER: 16937 SUBJECT: GRB 141004A: RATIR Late Time Optical and NIR Observations DATE: 14/10/21 21:58:12 GMT FROM: Owen Littlejohns at Az State U Owen Littlejohns (ASU), 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), Enrico Ramirez-Ruiz (UCSC), José A. de Diego (UNAM), Leonid Georgiev (UNAM), Jesús González (UNAM), Carlos Román-Zúñiga (UNAM), Neil Gehrels (GSFC), and Harvey Moseley (GSFC) report: We observed the field of GRB 141004A (D'Elia, et al., GCN 16878) 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 2014/10 21.31 to 2014/10 21.51 UTC (392.08 to 396.95 hours after the BAT trigger), obtaining a total of 3.89 hours exposure in the r, i and z bands. We continue to detect the source reported from the previous epoch of RATIR observations (Littlejohns, et al., GCN 16887). We obtain the following detections and upper limit (3-sigma): r 24.21 +/- 0.24 i 23.24 +/- 0.14 z > 21.47 These magnitudes are in the AB system and are not corrected for Galactic extinction in the direction of the GRB. These magnitudes suggest the source to remain brighter than expected if determined purely from a typical GRB power-law decay. This may corroborate the claim of re-brightening (Schulze, et al., GCN 16936), however, it may also indicate the detection of the host galaxy (de Ugarte Postigo, et al., GCN 16902). We also note that these magnitudes are broadly consistent with those observed by GROND at an approximate epoch of 32 hours after the initial Swift/BAT trigger (Schmidl, et al., GCN 16899). We thank the staff of the Observatorio Astronómico Nacional in San Pedro Mártir.