TITLE: GCN CIRCULAR NUMBER: 11838 SUBJECT: GRB 110328A / Swift J164449.3+573451: PAIRITEL NIR Upper Limits DATE: 11/03/30 03:07:14 GMT FROM: Adam Morgan at U.C. Berkeley A. N. Morgan, C.R. Klein, A. A. Miller, and J. S. Bloom (UC Berkeley) report: We observed the field of GRB 110328A / Swift J164449.3+573451 (Cummings et al., GCN 11823, Barthelmy et al., GCN 11824) with the 1.3m PAIRITEL located at Mt. Hopkins, Arizona. Observations began at 2011-03-29 08:32:46 UT, ~19.6 hours after the first Swift Trigger. In mosaics (effective exposure time of 0.39 hours) taken simultaneously in the J, H, and Ks filters, we do not detect any source at the optical/radio position (Cenko et al., GCN 11827, Leloudas et al., GCN 11830, Zauderer et al., GCN 11836, Volnova et al. GCN 11837). The preliminary photometry yields: post burst t_mid (hr) exp.(hr) filt U. Limit (3 sig) 19.9 0.39 J > 19.1 19.9 0.39 H > 18.2 19.9 0.39 Ks > 16.9 Further observations will be performed tonight. All magnitudes are given in the Vega system, calibrated to 2MASS. No correction for Galactic extinction has been made to the above reported values.