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We present the result of the analysis of the gravitational binary-lensing event OGLE-2005-BLG-018. The light curve of the event is characterized by two adjacent strong features and a single weak feature separated from the strong features. The light curve exhibits noticeable deviations from the best-fit model based on standard binary parameters. To explain the deviation, we test models including various higher-order effects of the motions of the observer, source, and lens. From this, we find that it is necessary to account for the orbital motion of the lens in describing the light curve. From modeling the light curve considering the parallax effect and Keplerian orbital motion, we are able to not only measure the physical parameters but also to find a complete orbital solution of the lens system. It is found that the event was produced by a binary lens located in the Galactic bulge with a distance of 6.7 ± 0.3 kpc from the Earth. The individual lens components with masses 0.9 ± 0.3 M ☉ and 0.5 ± 0.1 M ☉ are separated with a semi-major axis of a = 2.5 ± 1.0 AU and orbiting each other with a period P = 3.1 ± 1.3 yr. This event demonstrates that it is possible to extract detailed information about binary lens systems from well-resolved lensing light curves. [ABSTRACT FROM AUTHOR]

We report the extremely high-magnification (A > 1000) binary microlensing event OGLE-2007-BLG-514. We obtained good coverage around the double peak structure in the light curve via follow-up observations from different observatories. The binary lens model that includes the effects of parallax (known orbital motion of the Earth) and orbital motion of the lens yields a binary lens mass ratio of q = 0.321 ± 0.007 and a projected separation of s = 0.072 ± 0.001 in units of the Einstein radius. The parallax parameters allow us to determine the lens distance DL = 3.11 ± 0.39 kpc and total mass ML = 1.40 ± 0.18 M☼; this leads to the primary and secondary components having masses of M1 = 1.06 ± 0.13 M☼ and M2 = 0.34 ± 0.04 M☼, respectively. The parallax model indicates that the binary lens system is likely constructed by the main-sequence stars. On the other hand, we used a Bayesian analysis to estimate probability distributions by the model that includes the effects of xallarap (possible orbital motion of the source around a companion) and parallax (q = 0.270 ± 0.005, s = 0.083 ± 0.001). The primary component of the binary lens is relatively massive, with M1 = 0.9+4.6–0.3M☼ and it is at a distance of DL = 2.6+3.8–0.9 kpc. Given the secure mass ratio measurement, the companion mass is therefore M2 = 0.2+1.2–0.1M☼. The xallarap model implies that the primary lens is likely a stellar remnant, such as a white dwarf, a neutron star, or a black hole. [ABSTRACT FROM AUTHOR]