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Primary caustics and critical points behind a Kerr black hole


Sereno, M; de Luca, F (2008). Primary caustics and critical points behind a Kerr black hole. Physical Review D, 78(2):023008.

Abstract

The primary optical caustic surface behind a Kerr black hole is a four-cusped tube displaced from the line of sight. We derive the caustic surface in the nearly asymptotic region far from the black hole through a Taylor expansion of the lightlike geodesics up to and including fourth-order terms in m/b and a/b, where m is the
black hole mass, a the spin and b the impact parameter. The corresponding critical locus in the observer’s sky is elliptical and a point-like source inside the caustics will be imaged as an Einstein cross. With regard to lensing
near critical points, a Kerr lens is analogous to a circular lens perturbed by a dipole and a quadrupole potential.
The caustic structure of the supermassive black hole in the Galactic center could be probed by lensing of low
mass X-ray binaries in the Galactic inner regions or by hot spots in the accretion disk.

The primary optical caustic surface behind a Kerr black hole is a four-cusped tube displaced from the line of sight. We derive the caustic surface in the nearly asymptotic region far from the black hole through a Taylor expansion of the lightlike geodesics up to and including fourth-order terms in m/b and a/b, where m is the
black hole mass, a the spin and b the impact parameter. The corresponding critical locus in the observer’s sky is elliptical and a point-like source inside the caustics will be imaged as an Einstein cross. With regard to lensing
near critical points, a Kerr lens is analogous to a circular lens perturbed by a dipole and a quadrupole potential.
The caustic structure of the supermassive black hole in the Galactic center could be probed by lensing of low
mass X-ray binaries in the Galactic inner regions or by hot spots in the accretion disk.

Citations

11 citations in Web of Science®
12 citations in Scopus®
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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Institute for Computational Science
Dewey Decimal Classification:530 Physics
Language:English
Date:July 2008
Deposited On:13 Mar 2009 10:22
Last Modified:05 Apr 2016 13:07
Publisher:American Physical Society
ISSN:1550-2368
Publisher DOI:10.1103/PhysRevD.78.023008
Related URLs:http://arxiv.org/abs/0710.5923v2
Permanent URL: http://doi.org/10.5167/uzh-16760

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