Partial Coverage and Time Variability of Narrow-Line Intrinsic QSO Absorption Systems

It is possible to distinguish intrinsic'' absorption systems (gas clouds within the quasar environment) from intervening’’ systems (gas clouds unrelated to the quasar phenomenon) by considering certain observational properties. We find that the most direct determinations of the intrinsic nature of a system are time variability and partial coverage of the background light source by the absorption region. Both of these conditions are unlikely to occur in intervening systems. We present Keck and HIRES data which demonstrate both these phenomena. We also summarize a list of several other observational properties which appear to be indicative of ``intrinsic’’ systems.