TITLE: GCN CIRCULAR NUMBER: 8994 SUBJECT: GRB 090313: Gemini-S redshift DATE: 09/03/14 05:45:25 GMT FROM: Daniel Perley at U.C. Berkeley R. Chornock, D. A. Perley, S. B. Cenko, J. S. Bloom, B. Cobb (UC Berkeley), and J. X. Prochaska (UCO/Lick) report: We began a spectroscopic integration on the afterglow of GRB 090313 (Chornock et al., GCN 8979; Mao et al., GCN 8980) using Gemini-South (GMOS) starting at 04:20 UT on 2009-03-14, approximately 19 hours after the trigger. We conducted a series of two exposures of 600 seconds each using the R400 grating, covering a wavelength range of approximately 3900 to 8140 Angstroms. Additional exposures are in progress. We detect transitions corresponding to C IV, Al II, O I, Si II, Si IV, and Fe II, as well as a broad absorption feature which we associate with Lyman-alpha, at a common redshift of z=3.375. We also detect Si II* at this redshift, identifying this as the redshift of the GRB. While ruling out an association with the bright nearby SDSS galaxy, this redshift suggests an extraordinary late-time afterglow luminosity. We continue to encourage sustained late-time follow-up of this event, which given its continued brightness (Perley et al., GCN 8985; de Ugarte Postigo et al., GCN 8992) is likely to continue to be observable to small-aperture telescopes for an extended period of time. We thank the Gemini staff for conducting these observations.