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GCN Circular 8994

Subject
GRB 090313: Gemini-S redshift
Date
2009-03-14T05:45:25Z (15 years ago)
From
Daniel Perley at U.C. Berkeley <dperley@astro.berkeley.edu>
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.
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