A. J. Castro-Tirado (IAA-CSIC), A. F. Valeev (SAO-RAS), S. Jeong (SKKU),
R. S��nchez-Ram��rez (IAA-CSIC), V. V. Sokolov (SAO-RAS), P. Ferrero
(IAA-CSIC), J. C. Tello (IAA-CSIC), Y. Hu (IAA-CSIC), B.-B. Zhang
(IAA-CSIC), A. Pozanenko (IKI-RAS), S. R. Oates (U. of Warwick), S.
Geier (GTC) and G. Lombardi (GTC), on behalf of a larger collaboration,
Following the detection of GRB 160623A by Fermi (Vianello et al. GCNC
19553) and Konus-Wind (Frederiks et al. GCNC 19554), we observed the
optical afterglow of GRB 160623A (Pozanenko et al. GCNC 19561) with the
10.4m Gran Telescopio Canarias (GTC), gathering spectra at different
epochs: June 25 (1.9 days post-burst) and July 3/4, with both the R1000B
and R2500I grisms covering the range 3800-10000 A. At the position of
the afterglow, the reddest spectrum (2 x 1200s with R2500I) showed
H-alpha and [SII] in emission, from which we determine a redshift z =
0.367, confirming the value proposed by Malesani et al. (GCNC 19708).
The bluest range spectrum (1200s) also revealed a marginal detection of
H-beta (taking into account the high foreground Galactic extinction in
the line of sight). The faint continuum on the first epoch spectrum
extended down to 3800 A with no absorption lines being present.
Therefore we propose this is the redshift of the GRB 160623A host
We acknowledge excellent support from the GTC staff.