We use multi-wavelength microlensing measurements of a sample of 10 image pairs from 8 lensed quasars to study the structure of their accretion disks .
By using spectroscopy or narrow band photometry we have been able to remove contamination from the weakly microlensed broad emission lines , extinction and any uncertainties in the large-scale macro magnification of the lens model .
We determine a maximum likelihood estimate for the exponent of the size versus wavelength scaling ( r _ { s } \propto \lambda ^ { p } corresponding to a disk temperature profile of T \propto r ^ { -1 / p } ) of p = 0.75 ^ { +0.2 } _ { -0.2 } , and a Bayesian estimate of p = 0.8 \pm 0.2 , which are significantly smaller than the prediction of thin disk theory ( p = 4 / 3 ) .
We have also obtained a maximum likelihood estimate for the average quasar accretion disk size of r _ { s } = 4.5 ^ { +1.5 } _ { -1.2 } lt-day at a rest frame wavelength of \lambda = 1026 ~ { } { \mathrm { \AA } } for microlenses with a mean mass of M = 1 M _ { \sun } , in agreement with previous results , and larger than expected from thin disk theory .