TITLE: GCN CIRCULAR NUMBER: 22702 SUBJECT: GRB 180510B: VLT/X-shooter observations DATE: 18/05/11 11:34:10 GMT FROM: Andrea Rossi at INAF J. Palmerio (IAP, Paris), A. Rossi (INAF-OAS), D. Malesani (DAWN/NBI and DARK/NBI), N. R. Tanvir (Univ. Leicester), V. D'Elia (ASI-SSDC), A. de Ugarte Postigo (HETH/IAA-CSIC and DARK/NBI), S. D. Vergani (GEPI/Obs. Paris), D. Xu (NAOC), D. A. Kann (HETH/IAA-CSIC), J.P.U. Fynbo (DAWN/NBI), and B. Sbarufatti (PSU), report on behalf of the Stargate Consortium: We observed the optical afterglow of GRB 180510B (Tohuvavohu et al., GCN 22696; Schady et al., GCN 22701) with the ESO VLT/X-shooter spectrograph, covering the wavelength range 3000-21000 AA. The afterglow is clearly detected in the 10s acquisition images taken starting at 23:09 UT (~3.7 hours after the GRB trigger) with brightness R~19.8 (Vega), calibrated against USNO-B1 stars in the field. Spectroscopy started at 23:19 UT on 2018-05-10 (~3.9 hours after the GRB trigger) and consisted of 2 exposures of 600 s. Preliminary analysis of the spectrum reveals continuum flux down to 3600 AA, which sets an upper limit to the redshift z <~ 2 via the lack of any obvious DLA feature. In addition, we identify several absorption lines at a common redshift of z=1.305, the most prominent being ZnII/CrII, FeII, MgII, and MgI. Moreover, we also identify another absorption system at z=0.63 based on the detection of the MgII doublet. Therefore, we propose the most probable redshift of the GRB to be z=1.305, with an intervening system at 0.638. We acknowledge the excellent support from the ESO staff, particularly Boris Haeussler, Karleyne Silva and Emanuela Pompei in obtaining these observations.