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 1.2 +0.7 −0.4 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 = 0.3µm), of log[(rs,opt/cm) √ cos(i)/0.5] = 16.2±0.3. 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] = 15.3 +0.5 −0.6. Given an estimated black hole mass of 1.23 × 10 9 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. 1 Based on observations obtained with the Small and Moderate Aperture Research Telescope System