GCN Circular 19773
Subject
GRB 160804A: VLT/X-shooter redshift
Event
Date
2016-08-05T08:05:36Z (9 years ago)
From
Dong Xu at NAOC/CAS <dxu@nao.cas.cn>
D. Xu (NAOC), K. E. Heintz (DARK/NBI), D. Malesani (DARK/NBI and DTU
Space), K. Wiersema (U. Leicester), J. P. U. Fynbo (DARK/NBI), report on
behalf of a larger collaboration:
We observed the optical afterglow of GRB 160804A (Marshall et al., GCN
19761; Breeveld et al., GCN 19764) with the ESO VLT UT2 (Kueyen)
equipped with the X-shooter spectrograph. Observations started at 23:55
UT on 2016-08-04 (22.37 hr after the BAT trigger) and consisted of 4
spectra by 600 s each, covering the wavelength range 3500-20000 AA.
The continuum trace is well detected in our exposures, down to ~3100 AA.
The lack of any drop sets an upper limit to the redshift z < 1.55. A
number of superimposed absorption features are detected, which we
interpret as due to Mg I, Mg II, Fe II, Al II, as well as emission
features due to [O II], [O III], Halpha, Hbeta, Hgamma, [N II], [S II],
[S III], all at a common redshift z = 0.736. We thus conclude this is
the redshift of GRB 160804A.
We acknowledge excellent support from the ESO observing staff in
Paranal, in particular Jonathan Smoker, Leo Rivas, and Stephane Brillant.