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GCN Circular 31423

GRB 220107A: 6m BTA spectroscopic redshift
2022-01-09T20:07:17Z (2 years ago)
Alberto J. Castro-Tirado at IAA-CSIC <>
A. J. Castro-Tirado (IAA-CSIC), A. F. Valeev, A. Vinokurov and N. 
Burenkov (SAO-RAS), Y.-D. Hu, M.D. Caballero-Garcia, R. Sanchez-Ramirez 
and T-R. Sun (IAA-CSIC), on behalf of a larger collaboration, report:

Following the detection of GRB 220107A by Fermi/GRB (Fermi team GCNC 
31399), Swift/BAT (DeLaunay et al. GCNC 31402) and AstroSat/CZTI (Suresh 
et al. GCNC 31408), three spectra (600 s each, covering the 3700-8500 A 
spectral range) of the optical afterglow (Hosokawa et al. GCNC 31413, 
Siegel et al. GCNC 31415, Zhu et al. GCNC 31416, Pankov et al. GCNC 
31419, Moskvitin et al. GCNC 31422) were obtained by the 6m BTA 
(+SCORPIO-II) at the Special Astrophysical Observatory in Zelenchuk, 
Russia, on Jan 8, 23:25 UT (mid-exposure time, 1.36 days postburst). 
Several absorption lines (Fe II, Fe III, Mn II, Ni II and the Mg II 
doublet) are clearly identified, all consistent with a redshift z = 
1.246, which we propose to be the GRB redshift. We also confirm a 
redshift z = 0.309 �� 0.001 for the unrelated foreground galaxy reported 
by Pankov et al. (GCNC 31419), in agreement with the photometric redshift.

We acknowledge the excellent support of the BTA technical staff.
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