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GCN Circular 36176

Subject
GRB 240419A: VLT/UVES redshift of z = 5.178
Date
2024-04-19T10:34:58Z (3 months ago)
From
Benjamin Schneider at MIT <bschn@mit.edu>
Via
Web form
B. Schneider (MIT), L. Izzo (INAF-Napoli & DARK/NBI), A. Saccardi (GEPI/Obs. de Paris), D. B. Malesani (DAWN/NBI and Radboud Univ.),  J. T. Palmerio (GEPI, Obs. de Paris), A. de Ugarte Postigo (CNRS, OCA, LAM), V. D'Elia (ASI/SSDC & INAF-OAR), N. Gaspari (Radboud Univ.), P. Schady (Univ. of Bath), S. Covino (INAF/Brera), N. R. Tanvir (Univ. Leicester), A. J. Levan (Radboud Univ.), B. P. Gompertz (Birmingham), report on behalf of the Stargate collaboration:

We observed the optical afterglow of GRB 240419A (Siegel et al., GCN 36169; Schneider et al., GCN 36175) using the ESO VLT UT2 (Kueyen) equipped with the UVES high-resolution spectrograph. Observations were automatically performed via the rapid-response mode (RRM) system. The observations consisted of a series of spectra taken on April 19 with the first one starting at 02:15:42 UT (27.7 min after the GRB). The spectra cover a wavelength range from 3700 to 9300 AA and were obtained at a relatively high airmass of 2.4.

In the spectrum of 700 s, we only detect a continuum in the upper chip of the red arm (7770 to 9300 AA). From the detection of multiple absorption features, which we interpret as being due to SII, OI, Si II, Si II*, CII, CII*, Si IV, we infer a common redshift of z = 5.178. We conclude this is the redshift of the burst. This is consistent with the absence of flux in the blue dichroic, which covers the wavelength range from 3300 to 5000 AA, and which is entirely blue-ward of the Lyman break at z = 5.178. We also note the presence of additional absorption features likely due multiple intervening systems.

We acknowledge expert support from the ESO staff in Paranal, in particular Jonathan Smoker and Diego Parraguez.
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