GCN Circular 19109
Subject
GRB 160227A: NOT redshift
Date
2016-02-28T18:34:30Z (8 years ago)
From
Dong Xu at NAOC/CAS <dxu@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.