The X-Ray Continuum Emission Region in the Lensed Quasar SDSS J133907.23+131038.6 Is Much Smaller than the Accretion Disk

Abstract We analyze microlensing variability in 15 seasons of optical monitoring data and 4 epochs of new X-ray observations of the doubly imaged gravitationally lensed quasar SDSS J133907.23+131038.6 to place empirical constraints on the size and structure of that system’s X-ray and optical continuum emission regions. Employing a Bayesian Monte Carlo method, we analyzed ground-based optical light curves to constrain the half-light radius of the far-UV source log ( r 1 / 2 , FUV / cm ) = 15.7 8 − 0.28 + 0.26 at 1930 Å, the rest-frame center of the r band, assuming a 60° inclination angle. This size corresponds to ∼100 r g for a 4.0 × 10 8 M ⊙ black hole. We measured the half-light radius of the full band (0.2−8.0 keV) X-ray continuum emission region log ( r 1 / 2 , X full / cm ) = 14.3 2 − 0.31 + 0.23 , a size measurement that is consistent with the radius of the innermost stable circular orbit (ISCO) in the Schwarzschild metric. Two shifted Fe K α lines caused by microlensing are detected in the stacked spectrum of image A at 5.9 and 8.9 keV at >99% significance.