GCN Circular 32928
Subject
GRB 221110A: VLT/X-shooter redshift
Date
2022-11-10T05:18:41Z (a year ago)
From
Daniele B Malesani at Radboud U <d.malesani@astro.ru.nl>
L. Izzo (DARK/NBI), D. B. Malesani (Radboud Univ. and DAWN/NBI), S.
Vejlgaard Nielsen (DAWN/NBI), N. R. Tanvir (Univ. Leicester), J. P. U.
Fynbo (DAWN/NBI), D. Xu (NAOC) report on behalf of the Stargate
collabaration:
We observed the optical afterglow of GRB 221110A (Williams et al., GCN
32925; Lipunov et al., GCN 32924; Strausbaugh & Cucchiara, GCN 32926;
Pereyra et al., GCN 32927) using the ESO VLT UT3 (Melipal) equipped with
the X-shooter spectrograph. Our spectra cover the wavelength range
3000-25000 AA, and consist of 2 exposures by 600 s each. The observation
mid time was 2022 Nov 10.158 UT (1.33 hr after the GRB).
We clearly detect continuum over the wavelength range 6200-25000 AA. A
sharp break is visible around 6200 AA, which we identify as due to H I.
From detection of multiple absorption features, which we interpret as
due to Si IV, C IV, Fe II, O I, Si II, Al II, Al III, and many others,
we infer a redshift of z = 4.06. An intervening system is also detected
from Fe II and Mg II at z = 2.724.
We acknowledge excellent support from the ESO observing staff in
Paranal, in particular Michael Marsset and Florian Rodler.