GRB 241030A: Keck/LRIS spectroscopic redshift z = 1.411

Following the detection of GRB 241030A (Klingler et al., GCN 37956), we observed its optical counterpart (Klingler et al., GCN 37956; Watson et al., GCN 37957; Fernández-Rodríguez et al., GCN 37958) with the Low Resolution Imaging Spectrometer (LRIS; Oke et al. 1995) on the Keck I 10 m telescope. Observations started at 2024-10-30 06:47 UTC (about 1.0 hr after the burst), and consisted of 3 x 200 s exposures with the 600/4000 grism and 400/8500 grating. The spectrum shows a well-detected continuum throughout the complete range (3400-10,200 Ang). Numerous narrow absorption lines are present, including Mg II 2796, 2803 Ang doublets at redshifts of 0.456, 0.862, 1.302, and 1.411. We conclude that the redshift of the GRB is likely to be 1.411, but perhaps larger if the highest-redshift doublet is not associated with the interstellar medium in the host galaxy. The data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.