A Consistent Picture Emerges: A Compact X-ray Continuum Emission Region in the Gravitationally Lensed Quasar SDSS J0924+0219

TL;DR

This study uses multi-epoch microlensing data across optical, UV, and X-ray bands to precisely measure the sizes of emission regions in a gravitationally lensed quasar, revealing a compact X-ray source and a shallower disk temperature profile.

Contribution

It provides the first robust constraints on the X-ray and UV emission region sizes in SDSS J0924+0219 using combined multi-wavelength microlensing data, highlighting deviations from standard accretion disk models.

Findings

The soft X-ray emission region has a half-light radius between 5x10^13 and 10^15 cm.

The UV emission region size is between 10^14 and 3x10^15 cm.

The optical disk size exceeds the standard thin-disk prediction.

Abstract

We analyze the optical, UV, and X-ray microlensing variability of the lensed quasar SDSS J0924+0219 using six epochs of Chandra data in two energy bands (spanning 0.4-8.0 keV, or 1-20 keV in the quasar rest frame), 10 epochs of F275W (rest-frame 1089A) Hubble Space Telescope data, and high-cadence R-band (rest-frame 2770A) monitoring spanning eleven years. Our joint analysis provides robust constraints on the extent of the X-ray continuum emission region and the projected area of the accretion disk. The best-fit half-light radius of the soft X-ray continuum emission region is between 5x10^13 and 10^15 cm, and we find an upper limit of 10^15 cm for the hard X-rays. The best-fit soft-band size is about 13 times smaller than the optical size, and roughly 7 GM_BH/c^2 for a 2.8x10^8 M_sol black hole, similar to the results for other systems. We find that the UV emitting region falls in between the optical and X-ray emitting regions at 10^14 cm < r_1/2,UV < 3x10^15 cm. Finally, the optical size is significantly larger, by 1.5*sigma, than the theoretical thin-disk estimate based on the observed, magnification-corrected I-band flux, suggesting a shallower temperature profile than expected for a standard disk.