[vsnet-grb-info 19615] GRB 170714A: Bastille Day Burst redshift from OSIRIS/GTC

[GCN Circulars]

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  <deugarte at iaa.es>

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.