Gravitational time delays, observed in strong lens systems where the variable background
source is multiply imaged by a massive galaxy in the foreground, provide direct …

Gravitational lensing has developed into one of the most powerful tools for the analysis of
the dark universe. This review summarizes the theory of gravitational lensing, its main …

The radiative efficiency of active galactic nucleus (AGN) is commonly estimated based on
the total mass accreted and the total AGN light emitted per unit volume in the universe …

We use the microlensing variability observed for 11 gravitationally lensed quasars to show
that the accretion disk size at a rest-frame wavelength of 2500 Å is related to the black hole …

We use gravitational microlensing of the four images of the z= 0.658 quasar RXJ 1131–1231
to measure the sizes of the optical and X-ray emission regions of the quasar. The (face-on) …

Active galactic nuclei have been observed to vary stochastically with 10%–20% rms
amplitudes over a range of optical wavelengths where the emission arises in an accretion …

Microlensing perturbations to the flux ratios of gravitationally lensed quasar images can vary
with wavelength because of the chromatic dependence of the accretion disk's apparent size …

We present the results from nine years of optically monitoring the gravitationally lensed z
QSO= 0.658 quasar RX J1131− 1231. The R-band light curves of the four individual images …

Measuring time delays between the multiple images of gravitationally lensed quasars is now
recognized as a competitive way to constrain the cosmological parameters, and it is …

Strong gravitational lensing of quasars has the potential to unlock the poorly understood
physics of these fascinating objects, as well as serve as a probe of the lensing mass …