Abstract
Observations of several gravitationally lensed quasars revealed variations in the X-ray spectra of particular images. These variations are caused by microlensing caustics crossing the central emitting region of the quasar.
We study the phenomenon by simulating microlensing of a geometrically thin accretion disk around a central Kerr black hole. During the crossing of a caustic the iron K$\alpha$ line profile exhibits additional peaks and edges, depending on the mutual orientation of the caustic and the projected disk.
We demonstrate the correspondence of these spectral features with the geometry of the underlying emission. In support of our numerical results we derive analytical profiles of the generated features.
We illustrate additional features that arise in disks around non-extreme Kerr black holes, in which the innermost stable circular orbit lies above the horizon.