TITLE:   GCN CIRCULAR
NUMBER:  25565
SUBJECT: GRB 190829A: 10.4m GTC spectroscopy
DATE:    19/08/30 06:40:25 GMT
FROM:    Alberto J. Castro-Tirado at IAA-CSIC  <ajct@iaa.es>

A. F. Valeev (SAO-RAS), A. J. Castro-Tirado, Y.-D. Hu, and E. 
Fernandez-Garcia (IAA-CSIC), V. V. Sokolov (SAO-RAS), I. Carrasco and A. 
Castellon (UMA) D. Garcia Alvarez (GRANTECAN, IAC, ULL) and M. Rivero 
(GRANTECAN), on behalf of a larger collaboration, report:

Following the detection of GRB 190829A by Fermi (GCNC 25551) and Swift 
(Dichiara et al., GCN 25552), we obtained optical imaging and 
spectroscopy of the proposed optical counterpart (Xu et al. GCNC 25555, 
Lipunov et al. GCNC 25558, Kumar et al. GCNC 25560) covering the range 
3700-10000 A with the 10.4m GTC telescope equipped with OSIRIS in La 
Palma (Spain) starting on Aug 30, 03:00 UT.

On Aug 30, 3:00 UT, we measure i = 18.42 +/- 0.05. The GRB 190829A 
optical afterglow spectrum displays a red continuum consistent with the 
NOT results (Heintz et al. GCNC 25563). We find the Ca H & K doublet 
(3933 & 3969 A) in absorption in the afterglow spectrum, which also 
shows the emission lines of the underlying SDSS galaxy 
J025810.28-085719.2 at redshift z = 0.0785 +/- 0.005, thus supporting 
the physical association between GRB 190829A and the galaxy.

Thus, GRB 198029A is one of the nearest GRBs detected to date. 
Multiwavelength follow-up observations are encouraged.

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