The Structure of the X-ray and Optical Emitting Regions of the Lensed Quasar Q 2237+0305

TL;DR

This study uses gravitational microlensing to measure the sizes of X-ray and optical emission regions in a lensed quasar, revealing that X-ray regions are smaller and wavelength-dependent, consistent with accretion disk models.

Contribution

First measurement of X-ray and optical emission region sizes in Q 2237+0305 using microlensing, showing wavelength-dependent structure and relation to black hole mass.

Findings

Optical half-light radius is larger than X-ray regions.

X-ray emission region size correlates with black hole mass.

Hard X-ray component may be more compact than soft.

Abstract

We use gravitational microlensing to determine the size of the X-ray and optical emission regions of the quadruple lens system Q 2237+0305. The optical half-light radius, log(R_{1/2,V}/cm)=16.41\pm0.18 (at lambda_{rest}=2018 \AA), is significantly larger than the observed soft, log(R_{1/2,soft}/cm)=15.76^{+0.41}_{-0.34} (1.1-3.5 keV in the rest frame), and hard, log(R_{1/2,hard}/cm)=15.46^{+0.34}_{-0.29} (3.5-21.5 keV in the rest frame), band X-ray emission. There is a weak evidence that the hard component is more compact than the soft, with log(R_{1/2,soft}/R_{1/2,hard}) \sim 0.30^{+0.53}_{-0.45}. This wavelength-dependent structure agrees with recent results found in other lens systems using microlensing techniques, and favors geometries in which the corona is concentrated near the inner edge of the accretion disk. While the available measurements are limited, the size of the X-ray emission region appears to be roughly proportional to the mass of the central black hole.