[vsnet-grb-info 7710] GRB 090426 Keck LRIS redshift

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  9264
SUBJECT: GRB 090426 Keck LRIS redshift
DATE:    09/04/26 21:36:18 GMT
FROM:    Ryan Chornock at UC Berkeley  <chornock at astro.berkeley.edu>

E. Levesque (IfA, U. Hawaii), R. Chornock (UC Berkeley), L. Kewley (IfA, U.
Hawaii), J. S. Bloom (UC Berkeley), J. X. Prochaska (UCO/Lick), D. A. Perley, S.
B. Cenko, and M. Modjaz (UC Berkeley) report:

We obtained optical spectra of the afterglow of GRB 090426 (Cummings et al., GCN
9254) using LRIS on the Keck-I telescope, covering the wavelength range of
3000-9940 Angstroms.  Our first exposures started at 13:55 UT, 1.1 hrs after the
BAT trigger.  Preliminary analysis of the spectra reveals a set of absorption
lines at 4387, 5030, 5061, and 5592 Angstroms, which we identify as Lyman-alpha,
Si IV 1394, Si IV 1403, and the C IV 1548/1551 doublet at a common redshift of
2.609.  At this redshift, the observed T90 (Sato et al., GCN 9263) is 0.33 sec
in the rest frame of the burst.  This burst may be on the short end of the long
GRB population, similar to recent examples such as GRB 090423 (Krimm et al. GCN
9198, Palmer et al. GCN 9204, Thoene et al. GCN 9216, Tanvir et al. GCN 9219,
Krimm et al. GCN 9241), but we encourage further high-energy analyses of this event.