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We analyze variability in 15-season optical lightcurves from the doubly imaged lensed quasar SDSS J165043.44+425149.3 (SDSS1650), comprising five seasons of monitoring data from the Maidanak Observatory (277 nights in total, including the two seasons of data previously presented in Vuissoz et al.), five seasons of overlapping data from the Mercator telescope (269 nights), and 12 seasons of monitoring data from the US Naval Observatory, Flagstaff Station at lower cadence (80 nights). We update the 2007 time-delay measurement for SDSS1650 with these new data, finding a time delay of$\mathrm{\Delta }{t}_{\mathrm{AB}}=-{55.1}_{-3.7}^{+4.0}$days, with image A leading image B. We analyze the microlensing variability in these lightcurves using a Bayesian Monte Carlo technique to yield measurements of the size of the accretion disk atλ_rest= 2420 Å, finding a half-light radius of log(r_1/2/cm) =${16.19}_{-0.58}^{+0.38}$assuming a 60° inclination angle. This result is unchanged if we model 30% flux contamination from the broad-line region. We use the width of the Mgiiline in the existing Sloan Digital Sky Survey spectra to estimate the mass of this system’s supermassive black hole, findingM_BH= 2.47 × 10⁹M_⊙. We confirm that the accretion disk size in this system, whose black hole mass is on the very high end of theM_BHscale, is fully consistent with the existing quasar accretion disk size–black hole mass relation.

 

We studied the accretion disc structure in the doubly imaged lensed quasar SDSS J1339+1310 using r -band light curves and UV-visible to near-IR spectra from the first 11 observational seasons after its discovery. The 2009−2019 light curves displayed pronounced microlensing variations on different timescales, and this microlensing signal permitted us to constrain the half-light radius of the 1930 Å continuum-emitting region. Assuming an accretion disc with an axis inclined at 60° to the line of sight, we obtained log( r 1/2 /cm) = 15.4 −0.4 +0.93 . We also estimated the central black hole mass from spectroscopic data. The width of the C  IV , Mg  II , and H β emission lines, and the continuum luminosity at 1350, 3000, and 5100 Å, led to log( M BH / M ⊙ ) = 8.6 ± 0.4. Thus, hot gas responsible for the 1930 Å continuum emission is likely orbiting a 4.0 × 10 8   M ⊙ black hole at an r 1/2 of only a few tens of Schwarzschild radii.