X-Ray and Optical Microlensing in the Lensed Quasar PG 1115+080

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/λrest with -->λrest = 0.3 μm), of log{(rs, opt/cm)[cos(i)/0.5]½} = 16.6 ± 0.4$log b\{ (rs,opt/cm) [cos (i)/0.5]1/2b\} = 16.6 ± 0.4$ -->. The X-ray emission region (1.4-21.8 keV in the rest frame) has an effective half-light radius of -->log (r1/2,X/cm) = 15.6+ 0.6−0.9. Given an estimated black hole mass of -->1.2 × 109 M☉, corresponding to a gravitational radius of -->log (rg/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.