GCN Circular 35756
Subject
GRB 240218A: VLT/X-shooter redshift of z = 6.782
Date
2024-02-19T11:21:15Z (2 months ago)
From
Andrea Saccardi at Observatoire de Paris <andrea.saccardi@obspm.fr>
Via
Web form
A. Saccardi (GEPI/Obs. de Paris), D. B. Malesani (DAWN/NBI & Radboud Univ.), J. T. Palmerio (GEPI/Obs. de Paris & IAP), S. D. Vergani (GEPI/Obs. de Paris & IAP & INAF/OABr), E. Le Floc’h (CEA), L. Izzo (INAF/OACn & DARK/NBI), A. J. Levan (Radboud Univ. & Warwick Univ.), J. P. U. Fynbo (DAWN/NBI), P. D’Avanzo (INAF/OABr), A. Rossi (INAF/OAS), A. de Ugarte Postigo (OCA), report on behalf of the Stargate collaboration:
We observed the field of the Swift and Fermi GRB 240218A (Page et al., GCN 35742; D’Avanzo et al., GCN 35747; Malesani et al., GCN 35749; Veres et al., GCN 35755) 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 starting-time was 2024 Feb 19.179 UT (~26 hr after the trigger). We detect a clear continuum across the whole NIR arm. From the detection of multiple absorption features, which we interpret as due to SiII, FeII, AlII, CrII, ZnII, MgI, SiII*, FeII*, CIV and SiIV, we infer a redshift of z = 6.782.
We note that this is the highest GRB redshift measured accurately from metal absorption lines in a good S/N spectrum.
We encourage follow-up at all wavelengths.
We acknowledge the excellent support from the ESO staff in Paranal, in particular Jonathan Smoker, Rodrigo Romero and Pascale Hibon.