Predicting the Second Caustic Crossing in Binary Microlensing Events

Abstract

We fit binary lens models to the data covering the initial part of real microlensing events in an attempt to predict the time of the second caustic crossing. We use approximations during the initial search through the parameter space for light curves that roughly match the observed ones. Exact methods for calculating the lens magnification of an extended source are used when we refine our best initial models. Our calculations show that the reliable prediction of the second crossing can only be made very late, when the light curve has risen appreciably after the minimum between the two caustic-crossings. The best observational strategy is therefore to sample as frequently as possible once the light curve starts to rise after the minimum.

14 pages + 3 EPS figures, accepted for publication in MNRAS

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• The Many Possible Interpretations of Microlensing Event OGLE-2002-BLG-055
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• OGLE-2013-BLG-0578L: Microlensing Binary Composed of A Brown Dwarf And An M Dwarf
• Theory and practice of microlensing lightcurves around fold singularities
• OGLE-2016-BLG-0156: Microlensing Event With Pronounced Microlens-Parallax Effects Yielding Precise Lens Mass Measurement
• Determination of Stellar Ellipticities in Future Microlensing Surveys
• Evolutionary algorithm-based analysis of gravitational microlensing lightcurves
• Gaia20fnr: A binary-lens microlensing event with full orbital motion revealed by four space telescopes
• Angular Radii of Stars via Microlensing