Microlensing of Broad Absorption Line Quasars: Polarization Variability

Roughly 10% of all quasars exhibit Broad Absorption Line (BAL) features whichappear to arise in material outflowing at high velocity from the activegalactic nucleus (AGN). The details of this outflow are, however, very poorlyconstrained and the particular nature of the BAL material is essentiallyunknown. Recently, new clues have become available through polarimetric studieswhich have found that BAL troughs are more polarized than the quasar continuumradiation. To explain these observations, models where the BAL materialoutflows equatorially across the surface of the dusty torus have beendeveloped. In these models, however, several sources of the BAL polarizationare possible. Here, we demonstrate how polarimetric monitoring ofgravitationally lensed quasars, such as H 1413+117, during microlensing eventscan not only distinguish between two currently popular models, but can alsoprovide further insight into the structure at the cores of BAL quasars.Comment: 17 pages, 3 figures, accepted to PAS