TITLE: GCN CIRCULAR NUMBER: 19419 SUBJECT: GRB 160509A Gemini North redshift DATE: 16/05/10 16:43:15 GMT FROM: Nial Tanvir at U.Leicester N. R. Tanvir (U. Leicester), A. J. Levan (U. Warwick), S. B. Cenko (NASA/GSFC), D. Perley (DARK), A. Cucchiara (GSFC/STScI), K. Roth (Gemini), K. Wiersema (U. Leicester), A. Fruchter (STScI), T. Laskar (NRAO/U.C. Berkeley) report on behalf of a larger collaboration: We observed the optical counterpart of Fermi/LAT GRB 160509A (Levan et al. GCN 19410) with the Gemini North telescope on Mauna Kea, beginning at 2016-05-10 13:15 UT obtaining both optical spectroscopy with GMOS-N and near-IR imaging with NIRI. Our spectroscopy covers a wavelength range of about 5900 AA to 10100 AA, and reveals a single, well detected emission line which we interpret as [OII] 3727 AA at a redshift of z=1.17 (provisional analysis). Alternative possible identifications for this line are ruled out by the absence of other lines in the spectrum. Our infrared imaging shows the source, presumably some combination of host and afterglow, to be very red with K(Vega)~16.6 and J(Vega)~19.7 calibrated via 2MASS stars in the field. This would be consistent with a heavily dust extinguished event. We also note that the source is apparently unresolved in K-band seeing of 0.55 arcsec. We acknowledge the excellent support of the Gemini staff, in particular Michael Hoenig, and kind cooperation of the visiting observers, in expediting these observations. We also thank Gemini Head of Science, Nancy Levenson, for approving this request.