TITLE: GCN CIRCULAR NUMBER: 17523 SUBJECT: GRB 150301B: X-shooter spectroscopy DATE: 15/03/02 02:07:10 GMT FROM: Antonio de Ugarte Postigo at IAA-CSIC A. de Ugarte Postigo (IAA-CSIC, DARK/NBI), T. Kruehler (ESO), H. Flores (GEPI/Obs. de Paris), and J.P.U. Fynbo (DARK/NBI) report on behalf of a larger collaboration: We observed the afterglow of GRB 150301B (Lien et al. GCN 17515, Buckley et al. GCN 17518, Kann et al. GCN 17522) with X-shooter at the Very Large Telescope (Paranal Observatory, Chile). Observations started at 00:45 UT (5.12 hr after the burst), and consisted of 6x600 s exposures covering the spectral range between 3 000 and 18 000 Angstroms. In the acquisition image the afterglow is detected with R(Vega) = 21.0 mag, as compared to stars of the USNOB-1.0 catalogue. On a preliminary reduction we detect a weak continuum with absorption features of FeII, MgII and MgI at a common redshift of z = 1.5169, which we suggest as the redshift of the GRB. We acknowledge the excellent support provided by Paranal staff, and in particular Andrea Mehner, Tayyaba Zafar, and Marcelo Lopez.