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GCN Circular 31359

Subject
GRB 220101A: NOT redshift confirmation
Date
2022-01-01T23:43:26Z (2 years ago)
From
Daniele B Malesani at Radboud U <d.malesani@astro.ru.nl>
J. P. U. Fynbo (DAWN/NBI), A. de Ugarte Postigo (Obs. Cote d'Azur), D. 
Xu (NAOC), D. B. Malesani (Univ. Radobud and DAWN/NBI), B. 
Milvang-Jensen (DAWN/NBI), J. Viuho (NOT and DAWN/NBI), report on behalf 
of a larger collaboration:

We observed the optical counterpart of GRB 220101A (Tohuvavohu et al., 
GCN 31347; Arimoto et al., GCN 31350) using the Nordic Optical Telescope 
(NOT) equipped with the ALFOSC spectrograph. A spectrum with exposure 
time 4x1200 s (grism #20) was secured starting on 2022 Jan 1.81 UT (14.3 
hr after the GRB), under good conditions, and covering the wavelength 
range 5600-10200 AA.

A very clear trace is detected from the afterglow continuum. A deep, 
broad trough is detected around 6800 AA, which we interpret as due to 
damped Lyman alpha. A number of narrow absorption features are also 
clearly visible and allow to determine accurately the GRB redshift. We 
identify, among others, N V, S II, Si II, Si II*, O I, Ni II, C II, Si 
IV, C IV, Fe II, Fe II*, and Al II, all at a common redshift z = 4.618. 
Our results thus fully confirm the finding of Fu et al. (GCN 31353).

Nice year start for GRBs: happy 2022 to all GCN readers!
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