TITLE: GCN CIRCULAR NUMBER: 11998 SUBJECT: GRB 110503A: PAIRITEL NIR Detection DATE: 11/05/04 06:36:46 GMT FROM: Adam Morgan at U.C. Berkeley A. N. Morgan, and J. S. Bloom (UC Berkeley) report: We observed the field of GRB 110503A (Stamatikos et al., GCN 11991) with the 1.3m PAIRITEL located at Mt. Hopkins, Arizona under poor sky conditions. Observations began at 2011-05-04 02:46:35 UT, ~9.2 hours after the Swift Trigger. In mosaics (effective exposure time of 1.28 hours) taken simultaneously in the J and H filters, we marginally detect a source at the optical afterglow location (Stamatikos et al., GCN 11991; Leloudas et al., GCN 11994; Kann et al., GCN 11996). Our preliminary Ks band reduction is corrupted. The preliminary photometry yields: post burst t_mid (hr) exp.(hr) filt mag m_err 10.2 1.28 J 18.19 0.26 10.2 1.28 H 17.86 0.36 All magnitudes are given in the Vega system, calibrated to 2MASS. No correction for Galactic extinction has been made to the above reported values.