GCN Circular 28847
Subject
GRB 201103B (ZTF20acozryr/AT2020yxz): VLT/X-shooter redshift
Date
2020-11-06T04:58:38Z (4 years ago)
From
Dong Xu at NAOC/CAS <dxu@nao.cas.cn>
D. Xu (NAOC), J.-B. Vielfaure (APC, Paris University), D. A. Kann
(HETH/IAA-CSIC), D. B. Malesani (DTU Space), D. A. Perley (LJMU), A. J.
Levan (Radboud U. Nijmegen), S. Klose, B. Stecklum (both TLS Tautenburg),
K. Wiersema (Univ. Warwick), and A. de Ugarte Postigo (HETH/IAA-CSIC, DARK/NBI)
report on behalf of the Stargate Consortium:
We observed the transient ZTF20acozryr/AT2020yxz (Coughlin et al., GCN
28841), which has been proposed to be the optical afterglow of GRB
201103B (Svinkin et al., GCN 28844) using the ESO VLT UT3 (Melipal)
equipped with the X-shooter spectrograph. Our spectra cover the
wavelength range 3000-21000 AA, and consist of 4 exposures of 1200 s
each. The observation mid-time was 2020 Nov 6.116 UT (56.66 hr/2.361
days after the GRB).
In a 60 s image taken with the acquisition camera on Nov 6.0771 UT, we
detect the optical afterglow, for which we measure a preliminary
magnitude r ~ 20.7 mag (AB magnitude, calibrated against a nearby galaxy
from the Pan-STARRS catalog; Chambers et al. 2016, arXiv:1612.05560).
We clearly detect continuum over the entire wavelength range. From
detection of multiple absorption features, which we interpret as due to
CII, MgII, and multiple FeII lines, we infer a redshift z = 1.105. We
suggest this to be the redshift of the transient, which we hereby
confirm spectroscopically to be the afterglow of GRB 201103B.
We acknowledge excellent support from the ESO observing staff in Paranal,
in particular Ivan Aranda and Matias Jones.
[GCN OPS NOTE(04nov2020): Per author's request, Ivan Aranda and Matias Jones
were added to the last sentence.]
[GCN OPS NOTE(07nov20): Per author's request, Stecklum was added
to the author's list.]