TITLE: GCN CIRCULAR NUMBER: 15921 SUBJECT: GRB 140304A: NOT observations and redshift estimate DATE: 14/03/04 21:44:36 GMT FROM: Antonio de Ugarte Postigo at IAA-CSIC A. de Ugarte Postigo (IAA-CSIC, DARK/NBI), J. Gorosabel (EHU-UPV, IAA-CSIC), D. Xu (DARK/NBI), D. Malesani (DARK/NBI), A. Somero (NOT), B. Milvang-Jensen (DARK/NBI), M.I. Andersen (DARK/NBI), P. Jakobsson (U. Iceland) and J.P.U. Fynbo (DARK/NBI) report on behalf of a larger collaboration: We have observed the afterglow of 140304A (Gorbovskoy et al. GCN 15914, Evans et al. GCN 15915) with the Nordic Optical Telescope (NOT) equipped with ALFOSC. Observations started at 20:19 UT on March 4 (i.e., 6.95 hr after the burst) in r and g-bands. The afterglow is clearly detected in r-band at 20.5 mag, but undetected in g-band down to a 3-sigma limit of 21.5, pointing towards a high-redshift event at z ~ 5 if the Lyman break is between g and r-band. Further observations are ongoing.