Despite astrophysical importance of binary star systems , detections are limited to those located in small ranges of separations , distances , and masses and thus it is necessary to use a variety of observational techniques for a complete view of stellar multiplicity across a broad range of physical parameters .
In this paper , we report the detections and measurements of 2 binaries discovered from observations of microlensing events MOA-2011-BLG-090 and OGLE-2011-BLG-0417 .
Determinations of the binary masses are possible by simultaneously measuring the Einstein radius and the lens parallax .
The measured masses of the binary components are 0.43 M _ { \odot } and 0.39 M _ { \odot } for MOA-2011-BLG-090 and 0.57 M _ { \odot } and 0.17 M _ { \odot } for OGLE-2011-BLG-0417 and thus both lens components of MOA-2011-BLG-090 and one component of OGLE-2011-BLG-0417 are M dwarfs , demonstrating the usefulness of microlensing in detecting binaries composed of low-mass components .
From modeling of the light curves considering full Keplerian motion of the lens , we also measure the orbital parameters of the binaries .
The blended light of OGLE-2011-BLG-0417 comes very likely from the lens itself , making it possible to check the microlensing orbital solution by follow-up radial-velocity observation .
For both events , the caustic-crossing parts of the light curves , which are critical for determining the physical lens parameters , were resolved by high-cadence survey observations and thus it is expected that the number of microlensing binaries with measured physical parameters will increase in the future .