Related papers: Evidence for a source size of less than 2000 AU in…

Microlensing in Q2237+0305 between 1985 and 1995 (eg. Irwin et al. 1989; Corrigan et al. 1991; Ostensen et al. 1996) has been interpreted in two different ways; as microlensing by stellar mass objects of a continuum source having dimensions…

Recent OGLE (Optical Gravitational Lensing Experiment) and GLITP (Gravitational Lens International Time Project) monitoring data for QSO 2237+0305 (Huchra et al.) have been analyzed through a newly optimized N-body microlensing analysis…

We use published mid-IR and V-band flux ratios for images A and B of Q2237+0305 to demonstrate that the size of the mid-IR emission region has a scale comparable to or larger than the microlens Einstein Radius (ER, ~10^17 cm for solar mass…

The innermost regions of quasars can be resolved by a gravitational-lens {\lq}telescope{\rq} on scales down to a few AU. For the purpose, X-ray observations are most preferable, because X-rays originating from the innermost regions, can be…

We study three high magnification microlensing events, generally recognized as probable caustic crossings, in the optical light curves of the multiply imaged quasar Q 2237+0305. We model the light curve of each event as the convolution of a…

We present the continuation of our long-term spectroscopic monitoring of the gravitationally lensed quasar QSO 2237+0305. We investigate the chromatic variations observed in the UV/optical continuum of both quasar images A and B, and…

From the peak of a gravitational microlensing high-magnification event in the A component of QSO 2237+0305, which was accurately monitored by the GLITP collaboration, we derived new information on the nature and size of the optical V-band…

We study a recently observed gravitational microlensing peak in the V-band light curve of Q2237+0305A using a relatively simple, but highly consistent with the data (the best-fit reduced \chi^2 is very close to 1), physical model. The…

We use the high magnification event seen in the 1999 OGLE campaign light curve of image C of the quadruply imaged gravitational lens Q2237+0305 to study the structure of the quasar engine. We have obtained g'- and r'-band photometry at the…

Microlensing has proven an effective probe of the structure of the innermost regions of quasars, and an important test of accretion disk models. We present light curves of the lensed quasar HE 0435-1223 in the R band and in the ultraviolet,…

It is demonstrated that the 1988-90 microlensing events in image A of Q2237+0305 reported by Racine (1992) do not exclude microlensing models with very low average mass, making the source radius larger than the projected Einstein radius…

We present an extended optical monitoring of the quadruply-imaged gravitationally lensed quasar QSO 2237+0305, the Einstein Cross, including observations from different observatories in both hemispheres and using a new photometric…

Following the detection of a gravitational microlensing high magnification event (HME) in Q2237+0305A attempts have been made to place limits on the dimensions of the quasar continuum source. The analyses have studied either the observed…

Using a microlensing analysis of 11-years of OGLE V-band photometry of the four image gravitational lens Q2237+0305, we measure the inclination i of the accretion disk to be cos i > 0.66 at 68% confidence. Very edge on (cos i < 0.39)…

We develop a general method for analyzing the light curves of microlensed quasars and apply it to the OGLE light curves of the four-image lens Q2237+0305. We simultaneously estimate the effective source velocity, the average stellar mass,…

The monitoring of the gravitational lens Q2237+0305 carried out by the OGLE group during 1997--1999 is analyzed. The significant light amplifications in the C and A quasar components with maxima in mid- and late 1999, respectively, are…

We present new mid-IR observations of the quadruply lensed quasar Q2237+0305 taken with CanariCam on the Gran Telescopio Canarias. Mid-IR emission by hot dust, unlike the optical and near-IR emission from the accretion disk, is unaffected…

Geometrical optics provides an excellent description for quasar images crossing caustics which are formed by gravitational microlensing of objects like Q2237+0305. Within this approximation the source size can be estimated from the maximum…

The four-image gravitationally lensed quasar QSO 2237+0305 is microlensed by stars in the lens galaxy. The amplitude of microlensing variability can be used to infer the relative size of the quasar as a function of wavelength; this provides…

We use archival data of NASA's Chandra X-ray telescope to compile an X-ray light curve of all four images of the quadruply lensed quasar Q2237+0305 (z=1.695) from January 2006 to January 2007. We fit simulated point spread functions to the…