TITLE: GCN CIRCULAR NUMBER: 18524 SUBJECT: GRB 151029A VLT/X-shooter redshift DATE: 15/10/29 10:48:11 GMT FROM: Nial Tanvir at U.Leicester Nial R. Tanvir (Univ. Leicester), Thomas Kruehler (MPE), Daniele Malesani (DARK/NBI), Dong Xu (NAOC/CAS), Antonio de Ugarte Postigo (IAA-CSIC), Giovanna Pugliese (API/UvA) report on behalf of a larger collaboration: We observed the optical counterpart of GRB 151029A (Ukwatta et al., GCN 18522; Knust et al., GCN 18523) using the ESO Very Large Telescope UT2 equipped with the X-shooter spectrograph. Observations started on Oct 29.369 UT (1.02 hr after the GRB), that is at the end of the Chilean night, and were extended over twilight. The optical counterpart (Ukwatta et al., GCN 18522; Knust et al., GCN 18523) is clearly detected in our grz acquisition images. We detect a faint continuum throughout the spectral range of our observations, from about 3300A to 18000A, indicating an upper limit to the redshift of z~2. We also detect several weak absorption features that would be consistent with being MgII (2796/2804) and FeII (2344/2587/2600) lines at z=1.423, which we therefore report as the likely redshift for this GRB. We acknowledge expert support from the ESO observing staff, in particular Thomas Rivinius and Marcela Espinoza.