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GCN Circular 32079

GRB 220521A: NOT spectroscopic redshift
2022-05-22T02:04:13Z (2 years ago)
Daniele B Malesani at Radboud U <>
J. P. U. Fynbo (DAWN/NBI), Z. Zhu (NAO/CAS, HUST), D. Xu (NAOC/CAS), D. 
B. Malesani (Radboud Univ. and DAWN/NBI), T. Pursimo (NOT), K. 
Matilainen (NOT), report on behalf of a larger collaboration:

Spectroscopy of the optical counterpart of GRB 220521A (Dichiara et al., 
GCN 32076; Malesani & Pursimo, GCN 32078) was secured using the Nordic 
Optical Telescope (NOT) equipped with the ALFOSC spectrograph. Grism #4 
was used, covering the wavelength range 3650-9500 AA. Our first spectrum 
(1200 s exposure time) started on May 22.004 UT (0.76 hr after the GRB).

Preliminary analysis of the data, using archival calibration files, 
reveals a bright continuum in the red part, with a clear break around 
8150 AA, which we interpret as due to Lyman alpha. We also identify the 
Lyman limit, the Lyman forest, and several metal absorption features 
(among which Si II 1260, O I 1302, Si II 1304, C II 1334, Si IV 
1393,1402), which allow to determine z = 5.6.

The precision of the redshift can be improved after utilizing updated 
calibration files.
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