TITLE: GCN CIRCULAR NUMBER: 13890 SUBJECT: GRB 121024A: VLT/X-shooter redshift DATE: 12/10/24 07:10:59 GMT FROM: Nial Tanvir at U.Leicester N. R. Tanvir (U. Leicester), J. P. U. Fynbo (DARK/NBI), A. Melandri (INAF-OAB), A. J. Levan (U. Warwick), D. Xu (WIS), V. D'Elia (ASDC) report on behalf of the X-shooter GTO collaboration: We observed the afterglow of GRB 121024A (Pagani et al. GCN 13886) with the X-shooter spectrograph at the VLT. Observations began at 04:45 UT, approximately 1.8 hours after the initial detection of the burst. The afterglow is well detected in the acquisition image, and in the resulting spectrum we see a strong, broad damped-Lya absorption feature at ~4000A, combined with numerous narrow metal lines of CIV, SiII, SiIV, FeII, SII and AlII, as well as fine-structure lines associated with SiII*. These point to a common redshift of z=2.298 for GRB 121024A. We thank Maja Vuckovic, Giovanni Carraro, Marcelo Lopez and Felipe Gaete for their assistance in obtaining these observations, and Gianni Marconi and Gerry Gilmore for kindly allowing the ToO to be performed during their visitor mode run.