TITLE: GCN CIRCULAR NUMBER: 18028 SUBJECT: GRB 150716A: RATIR Optical Observations DATE: 15/07/16 17:23:37 GMT FROM: Alan M. Watson at Instituto de Astronomia UNAM Alan M. Watson (UNAM), Nat Butler (ASU), 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), 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 150716A (Kocevski et al., GCN 18027) 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 2015/07 16.30 to 2015/07 16.45 UTC (0.06 to 3.61 hours after the BAT trigger), obtaining a total of 2.21 hours exposure in the r and i bands. The field is crowded. Nevertheless, we detect a candidate optical afterglow within but close to the edge of the unenhanced Swift-XRT error circle at 18:33:57.20 -12:58:40.1 (J2000, ±0.5"). In comparison with the USNO-B1 and 2MASS catalogs, we obtain the following detections: r 20.34 ± 0.02 i 19.23 ± 0.02 At the moment, we have no information on fading, but further observations are planned. These magnitudes are in the AB system and are not corrected for Galactic extinction in the direction of the GRB. We thank the staff of the Observatorio Astronómico Nacional in San Pedro Mártir.