2020ApJ...895..125C

We use 13 seasons of R-band photometry from the 1.2 m Leonard Euler Swiss Telescope at La Silla to examine microlensing variability in the quadruply imaged lensed quasar WFI 2026-4536. The lightcurves exhibit ∼0.2 mag of uncorrelated variability across all epochs and a prominent single feature of ∼0.1 mag within a single season. We analyze this variability to constrain the size of the quasar's accretion disk. Adopting a nominal inclination of 60°, we find an accretion disk scale radius of log(r_s/cm)=15.74_–0.29^+0.34 at a rest-frame wavelength of 2043 Å, and we estimate a black hole mass of log(M_BH/M_☉)=9.18_–0.34^+0.39, based on the C IV line in VLT spectra. This size measurement is fully consistent with the quasar accretion disk size-black hole mass relation, providing another system in which the accretion disk is larger than predicted by thin-disk theory.