2008ApJ...689..755M

We analyzed the microlensing of the X-ray and optical emission of the lensed quasar PG 1115+080. We find that the effective radius of the X-ray emission is 1.3^+1.1_–0.5 dex smaller than that of the optical emission. Viewed as a thin disk observed at inclination angle i, the optical accretion disk has a scale length, defined by the point where the disk temperature matches the rest-frame energy of the monitoring band (kT=hc/λ_rest with λ_rest=0.3 µm), of log{cubl1}(r_s,opt/cm)cos(i)/0.5^1/2{cubr1}=16.6±0.4. The X-ray emission region (1.4-21.8 keV in the rest frame) has an effective half-light radius of log(r_1/2,X/cm)=15.6^+0.6_–0.9. Given an estimated black hole mass of 1.2x10⁹ M_☉, corresponding to a gravitational radius of log(r_g/cm)=14.3, the X-ray emission is generated near the inner edge of the disk, while the optical emission comes from scales slightly larger than those expected for an Eddington-limited thin disk. We find a weak trend supporting models with low stellar mass fractions near the lensed images, in mild contradiction to inferences from the stellar velocity dispersion and the time delays.