Program: GN-2015B-FT-9

Long Gamma-ray bursts may be associated with massive stars production and some of them have been detected up to GeV energies by the LAT instrument onboard the Fermi satellite. Due to the large energy emitted, these bursts are challenging our current knowledge of GRB progenitors. Determining the evolution of their X-ray/Optical afterglows, in combination with their host galaxy properties is key to understand their true nature. We propose to observe with GNIRS the host galaxy of GRB150314A (at z=1.758), which shows the possible presence of AGN activity. Alernatively, this GRB may present a new, unprecedent, case of late-time (> 1 month) emission, requiring a very long-living central engine. Measuring the strength of emission lines (redshifted into the NIR) rising from the host, in combination with large amount of ancillary data (including HST and Chandra), we will be able to finally determine the nature of GRB150314A. We request FT time because this GRB occurred after the 2015B deadline and will be visible during the following months.