GCN Circular 32648
Subject
GRB 221009A: Redshift from X-shooter/VLT
Date
2022-10-10T09:39:41Z (2 years ago)
From
Antonio de Ugarte Postigo at OCA <deugarte@oca.eu>
A. de Ugarte Postigo (OCA), L. Izzo (DARK/NBI), G. Pugliese
(Amsterdam Univ. and Leiden Observatory), D. Xu (NAOC),
B. Schneider (CEA Paris-Saclay), J.P.U. Fynbo (DAWN/NBI),
N.R. Tanvir (Univ. Leicester), D.B. Malesani (Radboud Univ.
and DAWN/NBI), A. Saccardi (GEPI, Observatoire de Paris),
D. A. Kann (Goethe Univ.), K. Wiersema (Lancaster Univ.),
B. P. Gompertz (Birmingham), C. C. Thoene (ASU-CAS) and
A. J. Levan (Radboud Univ.) report on behalf of the Stargate
collaboration:
We observed the afterglow of the extremely bright GRB221009A
(Dichiara et al., GCN 32632; Kennea & Williams, GCN 32635;
Bissaldi et al., GCN 32637; Veres et al., GCN 32636; Lesage et
al., GCN 32642) with X-shooter at ESO's UT3 of the Very Large
Telescope (Paranal, Chile). The observations started at
00:49:58.9 UT (11.55 hr after the GBM trigger and 10.66 hr
after the BAT trigger). The observation consisted of 4x600s with
a spectral coverage between 3000 and 21000 AA.
We detect a very red continuum with absorption features that
correspond to CaII, CaI and NaID at a redshift of z = 0.151. We
also detect multiple features due to the Milky Way���s interstellar
medium, due to the large Galactic column density of material
along this line of sight. At this redshift the event has an isotropic
equivalent energy of Eiso=2x10^54 erg (using the GBM fluence
reported in GCN 32642), barring saturation effects in the
Fermi/GBM fluence. This is within the upper end of GRB
energetics. Further follow-up is strongly encouraged.
We acknowledge the excellent support provided by the Paranal
staff, in particular A. Escorza and Zahed Wahhaj.