GCN Circular 42756
Subject
EP251118a: NOT spectroscopic redshift of z = 1.216
Event
Date
2025-11-19T09:17:33Z (2 days ago)
From
J. An <jiean0813@foxmail.com>
Via
Web form
J. An (NAOC), D. B. Malesani (DAWN/NBI and Radboud), L.B. He, D. Xu, X.Liu (NAOC), G. Corcoran (UCD), L. Cotter (UCD), A. J. Levan (Radboud and Warwick), P. G. Jonker (Radboud), L. Fuglsang (NOT), report on behalf of a large collaboration:
We observed the optical afterglow (Malesani et al., GCN 42751) of EP251118a (Jiang et al., GCN 42749) with the Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. A spectrum using grism #4 was secured starting on 2025 Nov 19.19 UT (11.9 h after the GRB). A total of 4 spectra of 1200 s each were obtained, covering the wavelength range 3500-9600 AA.
Preliminary reduction of the stacked spectrum shows a clear continuum down to at least 3700 AA. The lack of a Ly-alpha feature in the spectrum sets a redshift limit z < 2. A few narrow absorption features are detected, which we attribute to the Mg II doublet and several Fe II lines (2600, 2586, 2344), all at a common redshift of z = 1.216. We suggest this is the redshift of EP251118a.