TITLE: GCN CIRCULAR NUMBER: 19385 SUBJECT: GRB 160504A: NOT upper limits DATE: 16/05/04 22:22:05 GMT FROM: Thomas Kruehler at MPE Garching T. Kruehler (MPE Garching), A. de Ugarte Postigo (IAA-CSIC and DARK/NBI), and T. Kuutma (NOT) report on behalf of a larger collaboration: We observed the field of GRB 160504A (Malesani et al., GCN #19382) with the NOT equipped with ALFOSC. Imaging in the r, i and z-band filter started at 20:54:10 UT on 2016-05-04, 1.4 hr after the GRB trigger. We detect no sources in the enhanced XRT error circle given at http://www.swift.ac.uk/sper/685124/. Calibrating our images against magnitudes from field stars of the SDSS catalog, we measure preliminary upper limits of r > 23.3 mag i > 22.8 mag z > 22.0 mag These limits are not corrected for the expected foreground extinction corresponding to a reddening of E(B-V) = 0.01 mag (Schlafly & Finkbeiner 2011).