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M. Elvis (Harvard-Smithsonian Center for Astrophysics)
For well over 30 years quasars and AGN have presented an ever growing list of diverse and confusing phenomenology from optical to X-ray wavelengths: Broad emission lines, narrow absorption lines, broad absorption lines, `warm' soft X-ray absorbers, fluorescent X-ray Fe-K emission, and Compton scattering 'humps'. Progress has been slow, with each of these phenomena treated more or less in isolation.
I have proposed (Elvis 2000, ApJ in press) a simple geometric and kinematic model that allows all of these diverse phenomena to be understood as part of a single structure. Once in place, this structure suggests a natural physical interpretation, and constrains models. Once consequence is that the broad X-ray Fe-K line may not originate in the GR dominated part of an accretion disk, but in an outflowing wind with a special geometry.
With minor extensions the model also suggests explanations for the Baldwin effect (and its relatives), the "ionization" cones in AGN, and the lack of "quasar 2s". The need for a "molecular torus" in AGN is much weaker, if this model is correct.