GCN Circular 21119
L. Izzo (IAA-CSIC), A. de Ugarte Postigo (IAA-CSIC, DARK/NBI), D.A. Kann (IAA-CSIC), C.C. Thoene (IAA-CSIC), P. Pessev (GTC, IAC) and A. Tejero (GTC) report on behalf of a larger collaboration: We observed the afterglow of the GRB 170519A (Ukwatta et al., GCN 21106) using OSIRIS on the 10.4m GTC at the Roque de los Muchachos observatory (La Palma, Spain). The observation consisted of 3x1200s exposures using the R1000B grism, covering the range between 3700 and 7800 AA. The first spectrum started at 21:23 UT (16.22 hr after the burst). We detect clear absorption features due to Mg II, Mg I, Fe II, Fe II* and Ca II H&K lines at the common redshift of z = 0.818, which we identify as the redshift of the GRB.