Initial mass function of the Galactic bulge from binary microlensing events

Abstract.

The initial mass function of the Galactic bulge can be obtained from Hubble Space Telescope luminosity functions if the statistics of binary stellar systems is well constrained. Such statistics can be estimated using gravitational microlensing effect, which is sensitive to the masses of lensing objects. Current microlensing surveys are sensitive to microlensing signals produced by low-mass stars in the bulge. We propose to search for and analyze microlensing events containing binary lens or binary source in light curves of large microlensing surveys, including low-mass, unresolved binaries. We implemented a fully-automated approach in the search and characterization of new and previously identified events. With the consideration of detection efficiency, the large statistics of binaries gives constraints for the binary fraction and mass-ratio distribution. In this work, methods and results for some events with well-separated bumps are presented.