GCN Circular 32291
Subject
GRB 220627A: VLT MUSE redshift
Date
2022-06-29T13:06:24Z (2 years ago)
From
Daniele B Malesani at Radboud U <d.malesani@astro.ru.nl>
L. Izzo (DARK/NBI), V. D'Elia (ASI/SSDC, INAF/OAR), A. de Ugarte Postigo
(OCA), J. P. U. Fynbo (DAWN/NBI), D. A. Kann (IAA-CSIC), A. J. Levan
(Radboud Univ.), D. B. Malesani (Radboud Univ. and DAWN/NBI), A.
Saccardi (GEPI/Paris Obs.), C. C. Thoene (ASU-CAS), J. F. Agui Fernandez
(IAA-CSIC), S. de Wet (UCT), P. J. Groot (Radboud Univ., UCT, SAAO),
report on behalf of the Stargate consortium:
We observed the candidate optical afterglow (de Wet et al., GCN 32289)
of the Fermi GBM and LAT GRB 220627A (Roberts et al., GCN 32288; Di
Lalla et al., GCN 32283) using the ESO VLT equipped with the MUSE
integral-field spectrograph. Observations were carried out starting on
2022 June 29.06 UT (1.17 days after the trigger), and cover the
wavelength range 4800-9300 AA.
A broad trough is detected centered around 4960 AA, which we interpret
as due to DLA HI absorption. A number of metal lines are also detected,
which we identify as, among others, O I, O I*, Si II, Si II*, C II, C
II*, Si IV, C IV, Al II, at a common redshift z = 3.084. We also note
the presence of a (rich) intervening system at z = 2.665 (as identified
by, e.g., S IV, Si II, C IV, Fe II, Al II).
The redshift and luminosity of this object, together with its X-ray
emission (Evans et al., GCN 32284), make it very likely to be the
afterglow of GRB 220627A. Using the preliminary GBM fluence and spectral
parameters (Roberts et al., GCN 32288), we derive an
isotropic-equivalent quasi-bolometric gamma-ray energy of 3.6*10^54 erg
(0.1 keV - 100 MeV rest frame).
We thank the ESO staff at Paranal for carrying out or observations, in
particular Jonathan Smoker, Camila Navarrete, Rodrigo Palominos, and
Marco Berton.