Repeating microlensing events in the OGLE data

Abstract

Microlensing events are usually selected among single-peaked non-repeating light curves in order to avoid confusion with variable stars. However, a microlensing event may exhibit a second microlensing brightening episode when the source or/and the lens is a binary system. A careful analysis of these repeating events provides an independent way to study the statistics of wide binary stars and to detect extrasolar planets. Previous theoretical studies predicted that 0.5 - 2 % of events should repeat due to wide binary lenses. We present a systematic search for such events in about 4000 light curves of microlensing candidates detected by the Optical Gravitational Lensing Experiment (OGLE) towards the Galactic Bulge from 1992 to 2007. The search reveals a total of 19 repeating candidates, with 6 clearly due to a wide binary lens. As a by-product we find that 64 events (~2% of the total OGLE-III sample) have been miss-classified as microlensing; these miss-classified events are mostly nova or other types of eruptive stars. The number and importance of repeating events will increase considerably when the next-generation wide-field microlensing experiments become fully operational in the future.

11 pages, 4 figures (+ appendix A) and 3 tables

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• OGLE-III Microlensing Events and the Structure of the Galactic Bulge
• Modeling microlensing events with MulensModel
• OGLE-2009-BLG-092/MOA-2009-BLG-137: A Dramatic Repeating Event With the Second Perturbation Predicted by Real-Time Analysis
• Gaia Data Release 3: Microlensing Events from All Over the Sky
• Full orbital solution for the binary system in the northern Galactic disc microlensing event Gaia16aye
• Short-duration lensing events: II. Expectations and Protocols
• Three-dimensional Microlensing
• A companion on the planet/brown dwarf mass boundary on a wide orbit discovered by gravitational microlensing
• Bayesian Approach for Determining Microlens System Properties with High-Angular-Resolution Follow-up Imaging
• The OGLE-III planet detection efficiency from six years of microlensing observations (2003 to 2008)
• The complete catalogue of light curves in equal-mass binary microlensing
• VVV Survey Microlensing: Catalog of Best and Forsaken Events
• Blending from binarity in microlensing searches toward the Large Magellanic Cloud
• Deflection of light by the field of a binary system
• Microlensing and Variability in the Bulge of M31
• Binary Source Lensing and the Repeating OGLE EWS Events