Microlensing of Broad Absorption Line Quasars

The physical nature of the material responsible for the high--velocity, broad-absorption line features seen in a small fraction of quasar spectra has been the subject of debate since their discovery. This has been especially compounded by the lack of observational probes of the absorbing region. In this paper we examine the role of ``microlenses'' in external galaxies on observed variability in the profiles of broad absorption lines in multiply-imaged quasars. Utilizing realistic models for both the broad absorption line region and the action of an ensemble of microlensing masses, we demonstrate that stars at cosmological distances can provide an important probe of the physical state and structure of material at the heart of these complex systems. Applying these results to the macrolensed BAL quasar system, H1413+117, the observed spectral variations are readily reproduced, but without the fine-tuning requirements of earlier studies which employ more simplistic models.