TITLE: GCN CIRCULAR NUMBER: 14350 SUBJECT: GRB 130310A: RATIR Observations DATE: 13/03/28 15:50:17 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), Chris Klein (UCB), Ori Fox (UCB) J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (UCSC), 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 the Fermi-LAT detected GRB 130310A (Guiriec, et al., GCN 14282) 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. Data were taken in the r' and i' channels for a central 9.8 x 7.3 arcmin^2 portion of the IPN error region (Golenetskii, et al., GCN 14284), centered on RA, DEC = 141.90061, -17.10809 (J2000), in 2 epochs, 1.31-1.47 days after the Fermi trigger and 3.31-3.45 days after the Fermi trigger. We reach a limiting magnitude ~24 (AB) in both channels in both epochs. Data were captured in the Z, Y, J, and H bands over a larger field (14.8 x 12.5 arcmin^2), reaching a shallower limit (~22 AB). Of the XRT candidate afterglows (Sbarufatti, et al., GCN 14316), only source #5 is contained in our images. We detect that source in both epochs at a position RA, DEC = 141.881334, -17.147639 (+/-0.5" J2000): Epoch 1: r' = 23.6 +/- 0.1 i' = 23.6 +/- 0.2 Epoch 2: r' = 23.5 +/- 0.1 i' = 23.3 +/- 0.2 These magnitudes are in the AB system, not corrected for Galactic extinction in the direction of the GRB, and calibrated relative to USNO-B1. We find that source #5 has remained approximately constant in flux over a 2 day period. It has not faded and is therefore unlikely to be the afterglow of GRB 130310A. This source is not detected in the Z, Y, J, or H bands. We also note that we have searched for additional fading sources (delta_mag > 0.5) in all bands and have found none. We thank the staff of the Observatorio Astronómico Nacional in San Pedro Mártir.