GCN Circular 7791
D. A. Perley, J. S. Bloom (UC Berkeley), and J. X. Prochaska (UCO/Lick) report on behalf of a larger collaboration: Following the KAIT detection (Chornock et al., GCN 7789) of the afterglow candidate of GRB 080603 (Paizis et al., GCN 7790; Gomboc et al., GCN 7788) we began a spectroscopic sequence at Gemini-North using GMOS. We acquired 2x1200s longslit exposures starting at UT 13:24. We detect very strong resonance lines of MgII and FeII and the fine-structure transitions of FeII which establish the redshift of the GRB to be z=1.6880. In addition, we identify intervening MgII absorption systems at z=1.5635 (90% c.l.) and z=1.271 (100% c.l.) In addition, in a single acquisition exposure starting at UT 13:05:05 (107 minutes after the trigger) the object has a magnitude (relative to USNO B1.0) of R~19.7, suggesting it has not faded significantly since the observations of Gomboc et al. (GCN 7788). We thank Richard McDermid and the Gemini staff and for support.