TITLE: GCN CIRCULAR NUMBER: 27343 SUBJECT: GRB 200306A: RATIR Optical Observations DATE: 20/03/07 21:07:13 GMT FROM: Alan M Watson at UNAM Alan M. Watson (UNAM), Nat Butler (ASU), 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 200306A (Gropp et al., GCN Circ. 27326) 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 2020/03 7.27 to 2020/03 7.54 UTC (7.61 to 14.01 hours after the BAT trigger), obtaining a total of 4.31 hours exposure in the r and i bands. For a source within the Swift-XRT error circle, in comparison with the SDSS DR9 catalog, we obtain the following 3-sigma upper limits : r > 23.34 i > 23.71 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.