Microlensing Constraints on Accretion Disk Structure and Black Hole Spins and Floating Planets in Extragalactic Galaxies

Gravitational microlensing provides a unique probe of the innermost parts of quasar accretion disks, close to the event horizon of supermassive black holes. I will give a brief introduction of the technique. Using Chandra monitoring data from two Large Programs in Cycles 11 and 14/15, we have constrained the X-ray emission regions to be ~10 gravitational radii. We also identified two microlensing effects that can be used to constrain black hole spins and X-ray reflection regions for high redshift quasars. The first effect is the excess iron line equivalent widths of lensed quasars compared to normal AGN, and the second is the distribution of iron line peak energies of lensed quasars. A microlensing analysis of the iron line equivalent widths prefers high spin values and very steep iron line emissivity profiles for quasars at z~2. I will also discuss the prospect of measuring quasar spins with microlensing using the next generation of X-ray telescopes. Finally, I will also discuss the constraints on the lens populations, where a population of planets are needed to explain some observational results.

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