[vsnet-grb-info 17672] GRB 160227A: NOT redshift

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  19109
SUBJECT: GRB 160227A: NOT redshift
DATE:    16/02/28 18:34:30 GMT
FROM:    Dong Xu at NAOC/CAS  <dxu at nao.cas.cn>

D. Xu (NAOC/CAS), J. P. U. Fynbo, D. Malesani (DARK/NBI), A. de Ugarte 
Postigo (IAA-CSIC, DARK/NBI), T. Petrushevska (Stockholm U.), P. M. 
Sorensen, J. Saario, J. Telting (NOT) report on behalf of a larger 
collaboration:

We observed the field of GRB 160227A (Siegel et al., GCN 19098) using 
the 2.56m Nordic Optical Telescope (NOT) equipped with the ALFOSC 
camera. Observations started at 20:19:12 UT on 2016-02-27 (i.e., 0.784 
hr post-burst) and 2x120s R-band frames were obtained, followed by 
2x1800s+1x1200s spectroscopy (i.e., at a median time of ~1.87 hr 
post-burst) covering 3200A - 9000A, all in a seeing of ~2.0 arcsec.

The previously reported optical afterglow (e.g., Siegel et al., GCN 
19098; Gorbovskoy et al., GCN 19099) is clearly detected in our stacked 
R-band image, with R~19.3 mag calibrated with nearby USNO B1 stars.

Preliminary analysis of the spectrum shows a clear trough at the blue 
end of the spectral continuum, indicating Ly-alpha absorption from H I. 
We also detect several narrow absorption features, though at low 
signal-to-noise, which we interpret as due to, e.g., C II, Si II, O I, C 
II, Fe II, all consistent with a redshift of z = 2.38.