GCN Circular 29853
Subject
GRB 210420B: Redshift from GTC
Event
Date
2021-04-21T01:45:21Z (5 years ago)
From
Antonio de Ugarte Postigo at IAA-CSIC <deugarte@iaa.es>
A. de Ugarte Postigo (HETH/IAA-CSIC, DARK/NBI), M. Blazek,
C. Thoene, D. A. Kann, J. F Agui Fernandez (all HETH/IAA-CSIC),
and S. Geier (GTC, IAC) report:
We observed the afterglow of GRB 210420B (Moss et al. GCN
29844; Lipunov et al. GCN 29845; Oksanen GCN 29846; Hu et al.
GCN 29847; Sun et al. GCN 29848; Leonini et al. GCN 29851;
de Ugarte Postigo GCN 29852) with OSIRIS at the 10.4m GTC
telescope, at the Roque de los Muchachos Observatory (La Palma,
Spain). Observations consisted of 2x600 s spectroscopy with grism
R1000B, covering the spectral range between 3700 and 7800 AA.
The spectrum shows a strong continuum with weak absorption
features that we identify as due to FeII, MgII and MgI at a common
redshift of z = 1.400, which we interpret as the redshift of the GRB.