Gravitational microlensing and the structure of quasar outflows

We show that invaluable information on the structure quasar outflows can be obtained by considering micro-lensing (ML)-induced variability of absorption-line troughs in lensed quasars. Depending on the structure and geometry of the outflowing gas, such extrinsic line variability is manifested as changes to the equivalent width of the trough as well as line profile distortions. Here we consider several physically distinct outflow models having very similar spectral predictions, and show how ML-induced absorption-line variability can be used to distinguish between them. Possible merits from future systematic studies of these effects are exemplified.