Reconciling the Quasar Microlensing Disc Size Problem with a Wind Model of Active Galactic Nucleus

Abstract: Many analyses have concluded that the accretion disc sizes measured from the microlensing variability of quasars are larger than the expectations from the standard thin disc theory by a factor of $\sim4$. We propose a simply model by invoking a strong wind from the disc to flatten its radial temperature profile, which can then reconcile the size discrepancy problem. This wind model has been successfully applied to several microlensed quasars with a wind strength $s\lesssim1.3$ by only considering the inward decreasing of the mass accretion rate (where $s$ is defined through $\dot{M}(R)\propto({R}/{R_{0}})^{s}$ ). After further incorporating the angular momentum transferred by the wind, our model can resolve the disc size problem with an even lower wind parameter. The corrected disc sizes under the wind model are correlated with black hole masses with a slope in agreement with our modified thin disc model.