TITLE: GCN CIRCULAR NUMBER: 20043 SUBJECT: GRB 161014A: GTC spectroscopy DATE: 16/10/15 00:26:17 GMT FROM: Antonio de Ugarte Postigo at IAA-CSIC A. de Ugarte Postigo (IAA-CSIC, DARK/NBI), C. Thoene (IAA-CSIC), L. Izzo (IAA-CSIC), D.A. Kann (TLS Tautenburg), P. Pessev (IAC, ULL, GRANTECAN), A. Tejero (GRANTECAN) report on behalf of a larger collaboration: We observed the afterglow of GRB 161014A (Racusin et al., GCN 20035, Morita et al. GCN 20036, Guidorzi et al. GCN 20037, Xin et al. GCN 20038, Nakaoka et al. GCN 20039, D’Avanzo et al. GCN 20040, Mazaeva et al. GCN 20042) with OSIRIS at the 10.4m GTC telescope on La Palma (Spain). The observations started at 20:52 UT (with an average epoch at 8.8 hr after the burst) and consisted of 3 x 900 s spectra using grism R1000B, which covers the spectral region between 3700 and 7800 AA at a resolution of R ~ 1000. The spectrum has a low signal to noise ratio, but the preliminary reduction with archive calibrations still reveals prominent features due to Ly-alpha, SiII, CII, SiIV, CIV, AlII, and AlIII at a common redshift of z=2.823, which we identify as the redshift of the GRB.