We attempt to identify all microlensing parallax events for which the parallax fit improves ΔΧ2 > 100 relative to a standard microlensing model. We outline a procedure to identify three types of discrete degeneracies and find many new degenerate solutions in 16 previously published and 6 unpublished events. The lens of event OGLE-2003-BLG-84 may be a Jupiter-mass free-floating planet candidate based on a weak 3σ detection of finite-source effects. These events were examined for xallarap, which can mimic parallax. We find that 23% of these events are strongly affected by xallarap.
The mid-IR flux ratios of the two images of the gravitationally lensed quasar HE 1104-1805 show no wavelength dependence to within 3% across 3.6-8.0 microns, no time dependence over 6 months and agree with the broad emission line flux ratios. This indicates that the mid-IR emission likely comes from scales large enough to be little affected by microlensing and that there is little differential extinction between the images. We measure a revised time-delay between these two images. We also observed uncorrelated variations of ~ 0.05 mag/yr-1 which we attribute to microlensing of the optical emission from the accretion disk. The optical colors have also changed significantly in the sense that image A is now redder than image B, rather than bluer as it was in 1993.
Based on the microlensing variability of the two-image gravitational lens HE 1104-1805 observed between 0.4 and 8 microns, we have measured the size and wavelength-dependent structure of the quasar accretion disk. Modeled as a power law in temperature, we measure a B-band half-light radius of R = 6.7(+6.2)(-3.2)x10^15 cm (68% CL) and a logarithmic slope of 0.61(+0.21)(-0.17) (68% CL) for our standard model with a logarithmic prior on the disk size. Both the scale and the slope are consistent with simple thin disk models. The observed fluxes favor a slightly shallower temperature profile.
Using 11-years of OGLE V-band photometry of Q2237+0305, we measure the transverse velocity of the lens galaxy and the mean mass of its stars. We measure the inclination i of the accretion disk to be cos i > 0.63 at 68% confidence. Very edge on (cos i < 0.34) solutions are ruled out at 95% confidence. For the first time, we fully include the random motions of the stars in the lens galaxy in the analysis of the light curves. We find the best fit transverse velocity of the lens galaxy is ~ 420 km/s to the Northeast. There is no strong correlation between the direction of motion of the lens galaxy and the orientation of the disk. The mean stellar mass is 0.37(+1.07)(-0.26) solar masses after including a well-defined velocity prior. We measure the V-band radius of the accretion disk. We also show for the first time that analyzing subsets of a microlensing light curve, in this case the first and second halves of the OGLE V-band light curve, give mutually consistent physical results.