Constraints on Intrinsic UV Absorption in NGC 3783
  Results from an analysis of the intrinsic UV absorption in the Seyfert 1 galaxy NGC 3783 are presented. We focus on two new results that demonstrate techniques for deriving important constraints on the physical conditions and geometry of the absorbers. First, using variability in the spectrum, the emission-line profile is separated into distinct kinematic components and the effect on the interpretation of covering factors and column densities is demonstrated. Second, measurements of the 2s2p 3^P metastable levels of C^+2 derived from the C III* 1175-76 absorption multiplet are presented. New calculations of the metastable level populations are given and shown to provide a powerful diagnostic of the density (and thus location) and temperature in an absorber. 
Jack R. Gabel, Steven B. Kraemer and D. Michael Crenshaw