Microlensing can provide an important tool to study binaries, especially those composed of faint or dark objects. However, accurate analysis of binary-lens light curves is often hampered by the well-known degeneracy between close (s<1) and wide (s>1) binaries, which can be very severe due to an intrinsic symmetry in the lens equation. Here s is the normalized projected binary separation. In this paper, we propose a method that can resolve the close/wide degeneracy using the effect of a lens orbital motion on lensing light curves. The method is based on the fact that the orbital effect tends to be important for close binaries while it is negligible for wide binaries. We demonstrate the usefulness of the method by applying it to an actually observed binary-lens event MOA-2011-BLG-040/OGLE-2011-BLG-0001, which suffers from severe close/wide degeneracy. From this, we are able to uniquely specify that the lens is composed of K and M-type dwarfs located at ~3.5 kpc from the Earth.
@article{arxiv.1210.4269,
title = {Using Orbital Effects to Break the Close/wide Degeneracy in Binary-lens Microlensing Events},
author = {I. -G. Shin and T. Sumi and A. Udalski and J. -Y. Choi and C. Han and A. Gould and F. Abe and D. P. Bennett and I. A. Bond and C. S. Botzler and P. Chote and M. Freeman and A. Fukui and K. Furusawa and P. Harris and Y. Itow and C. H. Ling and K. Masuda and Y. Matsubara and N. Miyake and Y. Muraki and K. Ohnishi and N. Rattenbury and To. Saito and D. J. Sullivan and D. Suzuki and W. L. Sweatman and P. J. Tristram and K. Wada and P. C. M. Yock and M. K. Szymański and M. Kubiak and I. Soszyński and G. Pietrzyński and R. Poleski and K. Ulaczyk and P. Pietrukowicz and S. Kozłowski and J. Skowron and Ł. Wyrzykowski},
journal= {arXiv preprint arXiv:1210.4269},
year = {2015}
}