TITLE: GCN CIRCULAR NUMBER: 35960 SUBJECT: X-ray transient EP240315a: GTC/OSIRIS spectroscopic redshift confirmation DATE: 24/03/18 21:46:12 GMT FROM: P.G. Jonker at Radboud University <p.jonker@astro.ru.nl> J. Quirola-Vásquez (Radboud Univ.), P.G. Jonker (Radboud Univ.), A. J. Levan (Radboud Univ. & Warwick Univ.), F. E. Bauer (PUC), D. B. Malesani (DAWN/NBI and Radboud Univ.), Maria E. Ravasio (Radboud Univ.), M.A.P. Torres (IAC), A. M. García (GTC) on behalf of a larger collaboration: We observed the optical counterpart AT2024eju (Srivastav et al., GCN 35932) of the fast X-ray transient EP240315a reported by the Einstein Probe WXT instrument (Zhang et al., GCN 35931) and followed-up by its FXT instrument (Chen et al., GCN 35951), using the GTC/OSIRIS spectrograph. Our spectra cover the wavelength range 5100-10000 AA and consist of 3 exposures of 1200 seconds each. Observations started at 22:54:51 UT on Mar 16, 2024 (~27 hr after the X-ray trigger). We detect a faint trace, with the Lyman break and several absorption features which we identify as due to OIλ1302.17, SiIIλ1304.37, and SiIVλλ1393.76/1402.77. Therefore, we confirm the redshift identification of z = 4.859 determined by Saccardi et al. (GCN 35936) using VLT/X-shooter. We acknowledge the excellent support from the GTC staff. View this GCN Circular online at https://gcn.nasa.gov/circulars/35960. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...