TITLE: GCN CIRCULAR NUMBER: 21359 SUBJECT: GRB 170714A: Bastille Day Burst redshift from OSIRIS/GTC DATE: 17/07/21 06:36:26 GMT FROM: Antonio de Ugarte Postigo at IAA-CSIC A. de Ugarte Postigo (HETH/IAA-CSIC, DARK/NBI), D.A. Kann, L. Izzo, C.C. Thoene (HETH/IAA-CSIC), G. Lombardi S. Geier (GTC, IAC-ULL), A. Garcia, A. Perez (GTC) report: Following the detection of the afterglow (de Ugarte Postigo et al. GCN 21346) of the ultra-long GRB 170714A (D'Ai et al. GCN 21340, Kann et al. GCN 21345) we obtained further NIR and optical observations on 19 and 20 of July, with detections in r, i, z, and H-bands. An object is still observed at the position earlier reported, indicating an important host galaxy contribution. On 21 July, at 4:53 UT (5.69 days after the burst) we obtained spectroscopy of the afterglow/host galaxy with OSIRIS at the 10.4m GTC telescope (La Palma, Spain). Observations consisted of 4x900 s with grism R1000R, covering the range between 5100 and 10000 AA. The combined spectrum shows a weak trace with several superimposed emission lines, which we interpret as due to [OII], [OIII] and H-beta, through which we derive a redshift for the host galaxy, and hence for GRB 170714A, of 0.793.