TITLE: GCN CIRCULAR NUMBER: 42994 SUBJECT: GRB 251201B: SALT spectroscopic redshift z = 1.599 DATE: 25/12/04 23:55:00 GMT FROM: Daniele Bjørn Malesani at Cosmic Dawn Center, Niels Bohr Institute <daniele.malesani@nbi.ku.dk> D. B. Malesani (DAWN/NBI and Radboud), A. J. Levan (Radboud and Warwick), S. de Wet (DTU Space), A. de Ugarte Postigo (LAM), D. A. H. Buckley (SAAO), A. Martin-Carrillo (UCD), P. M. Vreeswijk (Radboud) report on behalf of a larger collaboration: We observed the optical afterglow of the Swift and Fermi GRB 251201B (Moss et al., GCN 42924; Palafox & Meegan, GCN 42965), using the Robert Stobie Spectrograph (RSS) installed on the 9.2 m Southern African Large Telescope (SALT) at the Sutherland observatory (South Africa). In a 10-s acquisition image, taken with the SALTICAM instrument on 2025 Dec 1.871 UT (4.47 hr after trigger), we measure a magnitude i = 19.25 +- 0.09 AB, calibrated against nearby stars from the Pan-STARRS catalog, and not corrected for Galactic extinction. A 2400-s spectrum was acquired using the PG0700 grating, covering the wavelength range 3600-7500 AA. Faint continuum is detected across the entire spectrum, setting a secure upper limit to the redshift z < 2. Towards the red end, we identify a few weak absorption features, which we match to Mg I 2852, Mg II 2804, 2796, Fe II 2600, 2587, 2383, all at a common redshift of z = 1.599, which we suggest to be the redshift of GRB 251201B. We acknowledge excellent support from the SALT observing staff, in particular Alexei Kniazev and Veronica Van Dyk. View this GCN Circular online at https://gcn.nasa.gov/circulars/42994. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...