Astrometric Resolution of Severely Degenerate Binary Microlensing Events

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Title: Astrometric Resolution of Severely Degenerate Binary Microlensing Events
Creators: Gould, Andrew; Han, Cheongho
Keywords: astrometry
Galaxy: stellar content
gravitational lensing
Magellanic Clouds
Issue Date: 2000-08-01
Publisher: American Astronomical Society
Citation: Andrew Gould and Cheongho Han, "Astrometric Resolution of Severely Degenerate Binary Microlensing Events," The Astrophysical Journal 538, no. 2 (2000), doi:10.1086/309180,
DOI: 10.1086/309180
Abstract: We investigate whether the "close/wide" class of degeneracies in caustic-crossing binary microlensing events can be broken astrometrically. Dominik showed that these degeneracies are particularly severe because they arise from a degeneracy in the lens equation itself rather than a mere "accidental" mimicking of one light curve by another. A massive observing campaign of five microlensing collaborations was unable to break this degeneracy photometrically in the case of the binary lensing event MACHO 98-SMC-1. We show that this degeneracy indeed causes the image centroids of the wide and close solutions to follow an extremely similar pattern of motion during the time when the source is in or near the caustic. Nevertheless, the two image centroids are displaced from one another, and this displacement is detectable by observing the event at late times. Photometric degeneracies therefore can be resolved astrometrically, even for these most severe cases.
ISSN: 1538-4357
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