GCN Circular 5715
David Osip (Las Campanas Observatory), H.-W. Chen (U Chicago), and J. X. Prochaska (UCO/Lick Observatory) report on behalf of a larger collaboration: "We observed the afterglow of GRB061007 reported by Rykoff & Rujopakarn (GCN 5706) and confirmed by Mundel et al. (GCN5708) and Bersier et al., using the LDSS3 with a 0.75-arcsec slit on the Magellan Clay telescope at the Las Campanas Observatory. The observations started at 03:54:00 UT on October 8, 2006, ~ 18 hours after the inital Swift/BAT trigger, and were carried out under a mean seeing condition of 0.75 arcsec in a sequence of five 1200-sec exposures. The final stacked spectrum covers the spectral range from 3900 Ang to 6500 Ang with a spectral resolution element of 2.4 Ang. In the spectrum, we identify a strong MgII absorption system, accompanied with FeII 2344 and 2600 transitions) at z=1.261. We consider this the likely redshift of GRB061007, given the absence of a strong Lya feature (or any other strong metal-line transitions) in our spectrum. We also report an intervening MgII system at z=1.06. Further analysis is underway. This message may be cited."