Shadow Geometry of Kerr Naked Singularities

Author:

Nguyen BaoORCID,Christian PierreORCID,Chan Chi-kwanORCID

Abstract

Abstract Direct imaging of supermassive black holes (SMBHs) at event horizon-scale resolutions, as recently done by the Event Horizon Telescope, allows for testing alternative models to SMBHs such as Kerr naked singularities (KNSs). We demonstrate that the KNS shadow can be closed, open, or vanishing, depending on the spins and observational inclination angles. We study the critical parameters where the KNS shadow opens a gap, a distinctive phenomenon that does not happen with the black hole shadow. We show that the KNS shadow can only be closed for dimensionless spin a ≲ 1.18 and vanishing for a ≳ 1.18 for certain ranges of inclination angles. We further analyze the effective angular momentum of photon orbits to demonstrate the fundamental connections between light geodesics and the KNS shadow geometry. We also perform numerical general relativistic ray-tracing calculations, which reproduce the analytical topological change in the KNS shadow, and illustrate other observational features within the shadow due to the lack of an event horizon. By comparing the geometric features of the KNS shadow with black hole shadow observations, the topological change in the shadow of KNSs can be used to test the cosmic censorship hypothesis and KNSs as alternative models to SMBHs.

Funder

National Science Foundation

Publisher

American Astronomical Society

Subject

Space and Planetary Science,Astronomy and Astrophysics

Cited by 3 articles. 订阅此论文施引文献 订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献

1. Spherical orbits around Kerr–Newman and Ghosh black holes;General Relativity and Gravitation;2024-07

2. Conservation of distortion of gravitationally lensed images;Physical Review D;2024-06-03

3. A rotating modified JNW spacetime as a Kerr black hole mimicker;Journal of Cosmology and Astroparticle Physics;2023-11-01

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