TITLE:   GCN CIRCULAR
NUMBER:  23708
SUBJECT: GRB 190114C: refined redshift by the 10.4m GTC
DATE:    19/01/15 06:38:04 GMT
FROM:    Alberto Castro-Tirado at Inst.de Astro. de Andalucia  <ajct@iaa.es>

A. J. Castro-Tirado. Y. Hu, E. Fernandez-Garcia (IAA-CSIC), A. Valeev, 
V. Sokolov (SAO-RAS), S. Guziy (Univ. of Nikolaev), S. Oates (U. 
Warwick) S. Jeong (SKKU), S. B. Pandey (ARIES), I. Carrasco (Univ. de 
Málaga) and D. Reverte-Paya (GRANTECAN, IAC, ULL), on behalf of a larger 
collaboration, report:

"Following the detection of the ultra-bright GRB 190114C (Gropp et al. 
GCN 23688, Hamburg et al. GCN 23707), also recorded at very-high 
gamma-ray energies (Mirzoyan et al. GCN 23701), optical spectroscopy of 
the reported optical afterglow (Gropp et al., GCN 23688; Tyurina et al. 
GCN 23690; Lipunov et al. GCN 23693; Selsing et al., GCN 23695; Izzo et 
al., GCN 23699; Bolmer et al., GCN 23702) has been undertaken at the 
10.4m GTC telescope (+OSIRIS) at the Spanish island of La Palma starting 
on Jan 14, 23:32 UT (2.6 hr post-burst). The two spectra (600s each, at 
high airmass) covered the range 3,700-9.600 A and the detection of Ca H 
& K lines and the Na I doublet (as well as other Fraunhofer lines) 
confirms the redshift value reported by Selsing et al. (GCN 23695) which 
we refine to z = 0.4245 +/- 0.0005, supporting the association with the 
galaxy detected in the Pan-STARRS archival data (de Ugarte Postigo et 
al. GCN 23692).

We acknowledge the excellent support of the GTC staff."