GCN Circular 46290
Subject
GRB 261114A: VLT/FORS2 spectroscopic redshift z = 3.716
Event
Date
2026-11-15T10:23:11Z (6 hours ago)
From
Andrea Saccardi at CEA/Irfu <andrea.saccardi@cea.fr>
Via
Web form
A. Saccardi (CEA/Irfu), J. An (NAOC), G. Corcoran (UCD), D. B. Malesani (DAWN/NBI and Radboud), E. Le Floc’h (CEA/Irfu), H. Fausey (Baylor), S. D. Vergani (Observatoire de Paris/LUX) report on behalf of the Stargate collaboration:
We observed the optical counterpart (Wu et al., GCN 46269; Zhao et al., GCN 46272; Li et al., GCN 46273; Li et al., GCN 46277; Schneider et al., GCN 46278) of the SVOM/ECLAIRs GRB 261114A (Li et. al., GCN 46267) using the ESO VLT UT1 (Antu) equipped with the FORS2 spectrograph.
In a 60 s I-band exposure taken with the acquisition camera (18.07 hr after the SVOM trigger), the counterpart is detected with a magnitude i = 22.6 +/- 0.2 (AB), calibrated against nearby objects from the SkyMapper catalog, and not corrected for Galactic extinction.
Our observation started on 2026 November 15 at 03:44:31 UT (18.19 hr after the SVOM trigger). A series of 3 spectra of 960 s each were obtained with the 600RI grism, covering the wavelength range 5300-8450 AA.
In a preliminary reduction of the spectra, we clearly detect a continuum over the entire wavelength range. A trough is visible at around ~5730 AA, which we interpret as due to Lyman alpha at z ~ 3.7. From the detection of multiple narrow absorption features, including Si II, Si IV, and C IV, we infer a redshift of z = 3.716.
We acknowledge excellent support from the ESO staff in Paranal.