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Superluminal Caustics of Close, Rapidly Rotating Binary Microlenses

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Title: Superluminal Caustics of Close, Rapidly Rotating Binary Microlenses
Creators: Zheng, Zheng; Gould, Andrew
Keywords: gravitational lensing
binaries: general
Issue Date: 2000-10-01
Publisher: American Astronomical Society
Citation: Zheng Zheng and Andrew Gould, "Superluminal Caustics of Close, Rapidly Rotating Binary Microlenses," The Astrophysical Journal 541, no. 2 (2000), doi:10.1086/309468
DOI: 10.1086/309468
Abstract: The two outer triangular caustics (regions of infinite magnification) of a close binary microlens move much faster than the components of the binary themselves, and can even exceed the speed of light. When ε ~> 1, where ε_c is the caustic speed, the usual formalism for calculating the lens magnification breaks down. We develop a new formalism that makes use of the gravitational analog of the Liénard-Wiechert potential. We find that as the binary speeds up, the caustics undergo several related changes: First, their position in space drifts. Second, they rotate about their own axes so that they no longer have a cusp facing the binary center of mass. Third, they grow larger and dramatically so for ε >> 1. Fourth, they grow weaker roughly in proportion to their increasing size. Superluminal caustic-crossing events are probably not uncommon, but they are difficult to observe.
ISSN: 1538-4357
URI: http://hdl.handle.net/1811/48180
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