Kerr black holes as retro-MACHOs

Abstract

Gravitational lensing is a well known phenomenon predicted by the General Theory of Relativity. It is now a well-developed observational technique in astronomy and is considered to be a fundamental tool for acquiring information about the nature and distribution of dark matter. In particular, gravitational lensing experiments may be used to search for black holes. It has been proposed that a Schwarzschild black hole may act as a retro-lens (Holz & Wheeler \cite{hw}) which, if illuminated by a powerful light source (e.g. the Sun), deflects light ray paths to large bending angles so that the light may reach the observer. Here, by considering the strong field limit in the deflection angle and confining our analysis to the black hole equatorial plane, we extend the Holz-Wheeler results to slowly spinning Kerr black holes. By considering the Holz-Wheeler geometrical configuration for the lens, source and observer we find that the inclusion of rotation does not substantially change the brightness of the retro-lensing images with respect to the Schwarzschild case. We also discuss the possibility that the next generation space-based telescopes may detect such retro-images and eventually put limits on the rotational parameter of the black hole.

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Cited by in corpus (20)

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• Braneworld black hole gravitational lens: Strong field limit analysis
• Mirages around Kerr black holes and retro-gravitational lenses
• Direct Measurements of Black Hole Charge with Future Astrometrical Missions
• Testing the No-Hair Theorem with Observations of Black Holes in the Electromagnetic Spectrum
• Dynamics of a Charged Particle Around a Slowly Rotating Kerr Black Hole Immersed in Magnetic Field
• Gravitational Lensing by Black Holes: a comprehensive treatment and the case of the star S2
• Retrolensing by a charged black hole
• Retrolensing by a wormhole at deflection angles $\pi$ and $3\pi$
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• Retrolensing by two photon spheres of a black-bounce spacetime
• Estimating the parameters of the Sgr A* black hole
• Gravitational lensing by using the 0th order of affine perturbation series of the deflection angle of a ray near a photon sphere
• Gravitational lensing of transient neutrino sources by black holes
• Retrolensing by light rays slightly inside and outside of a photon sphere around a Reissner-Nordström naked singularity
• Never bet against Einstein
• Kerr black holes as circular polarizers