2006ApJ...648...67P

PG 1115+080 is a quadruply lensed quasar at z=1.72 whose image positions are well fit by simple models of the lens galaxy (at z=0.31). At optical wavelengths, the bright close pair of images exhibits a modest flux ratio anomaly (factors of ∼1.2-1.4 over the past 22 yr) with respect to these same models. We show here that as observed in X-rays with Chandra, the flux ratio anomaly is far more extreme, roughly a factor of 6. The contrasting flux ratio anomalies in the optical and X-ray band confirm the microlensing hypothesis and set a lower limit on the size of the optical continuum emission region that is ∼10-100 times larger than expected from a thin accretion disk model.