TITLE:   GCN CIRCULAR
NUMBER:  35007
SUBJECT: GRB 231111A: TNG tentative redshift
DATE:    23/11/13 10:40:29 GMT
FROM:    Paolo D'Avanzo at INAF-OAB <pda.davanzo@gmail.com>

P. D'Avanzo (INAF-OAB), V. D'Elia (ASI/SSDC & INAF/OAR), D. B. Malesani (DAWN/NBI & Radboud Univ.), A. Melandri (INAF/OAR) , M. Cecconi, C. P. Padilla-Torres (INAF/TNG) report on behalf of the CIBO collaboration:

We report observations of GRB 231111A (Melandri et al. GCN Circ. 34981) with the 3.6m Telescopio Nazionale Galileo (TNG) equipped with DOLORES.

We acquired a spectrum of the optical source reported by Melandri et al. (GCN Circ. 34981). We obtained 2x1200 s with the LR-B grism, for a total exposure of 2400 s, covering the wavelength range 3500 - 8000 AA. The observations started on 2023-11-11 at 19:31:33 UT (i.e. about 5.2 hours after the GRB detection).  

The reduced spectrum is rather noisy and extends down to at least 3600 AA, indicating that the redshift is likely lower than z ~ 2. From preliminary reduction and calibration we tentatively infer a redshift of z ~ 1.39 from the possible detection of MgII 2796,2803. 
Further analysis is ongoing.