A Robust Determination of the size of quasar accretion disks using gravitational microlensing

TL;DR

This study uses gravitational microlensing data from multiple lensed quasars to accurately measure the average size of quasar accretion disks, revealing they are significantly larger than standard theoretical models predict.

Contribution

It provides a robust, large-sample measurement of quasar accretion disk sizes using microlensing, confirming previous findings and challenging standard thin disk model predictions.

Findings

Average quasar accretion disk size is about 4 light days.

Measured sizes are roughly five times larger than standard model predictions.

Results are consistent across individual quasars and the combined sample.

Abstract

Using microlensing measurements from a sample of 27 image-pairs of 19 lensed quasars we determine a maximum likelihood estimate for the accretion disk size of an {{\em}average} quasar of $r_s=4.0^{+2.4}_{-3.1} $ light days at rest frame $<\lambda>=1736$\AA\ for microlenses with a mean mass of $<M>=0.3M_\odot$. This value, in good agreement with previous results from smaller samples, is roughly a factor of 5 greater than the predictions of the standard thin disk model. The individual size estimates for the 19 quasars in our sample are also in excellent agreement with the results of the joint maximum likelihood analysis.