[vsnet-grb-info 10547] GRB 110422A: tentative redshift from TNG

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  11977
SUBJECT: GRB 110422A: tentative redshift from TNG
DATE:    11/04/26 15:51:06 GMT
FROM:    Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst  <malesani at dark-cosmology.dk>

D. Malesani (DARK/NBI), D. Fugazza (INAF/Brera), P. D'Avanzo 
(INAF/Brera), V. D'Elia (ASI/ASDC), A. Melandri (INAF/Brera), S. 
Piranomonte (INAF/Roma), J.P.U. Fynbo (DARK/NBI), M. Cecconi (INAF/TNG), 
G. Mainella (INAF/TNG), report on behalf of a larger collaboration:

We observed the afterglow of GRB 110422A (Mangano et al., GCN 11957; 
Klunko et al., GCN 11958) with the Italian TNG located in La Palma. A 
single 700 s spectroscopic exposure could be taken due to rising 
humidity (see also Melandri et al., GCN 11963). Observations started on 
2011 April 22.998 UT (8.25 hr after the GRB). The adopted grism was 
LR-B, covering the wavelength range 3600-8200 AA.

We detect a clear absorption feature at 4290 AA. Interpreting this as 
the (unresolved) CIV doublet yields a redshift of z = 1.77. At the same 
redshift we find a few other lines which we interpret as due to Si IV 
and Fe II. We thus propose z = 1.77 to be the redshift of GRB 110422A.