A Strong X-Ray Flux Ratio Anomaly in the Quadruply Lensed Quasar PG 1115+080

Abstract

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 years) 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.