Gravastar Shadows

Abstract

Direct observation of black holes is one of the grand challenges in astronomy. If there are super-compact objects which possess unstable circular orbits of photons, however, it may be difficult to distinguish them from black holes by observing photons. As a model of super-compact objects, we consider a gravastar (gravitational-vacuum-star) which was originally proposed by Mazur and Mottola. For definiteness, we adopt a spherical thin-shell model of a gravastar developed by Visser and Wiltshire, which connects interior de-Sitter geometry and exterior Schwarzschild geometry. We find that unstable circular orbits of photons can appear around the gravastar. Then, we investigate the optical images of the gravastar possessing unstable circular orbits, with assuming the optically transparent surface of it and two types of optical sources behind the gravastar: (i) an infinite optical plane and (ii) a companion star. The main feature of the image of (i) is that a bright disk and a dark thick ring surrounding the disk appear in the center of the region which would be completely dark if the compact object was not the gravastar but Schwarzschild black hole. Also in the case (ii), a small disk and arcs around the disk appear in the region which would be completely dark for the lensing image by Schwarzschild black hole. Because characteristic images appear inside the gravastar in both cases, we could tell the difference between a black hole and a gravastar with high-resolution VLBI observations near future.

9 pages, 11 figures

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Cited by in corpus (75)

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• Charged Thin-shell Gravastars in Noncommutative Geometry
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• Study of Gravastars in Rastall Gravity
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• A model for a dark matter core at the galactic center
• Shadow of a naked singularity
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• Stable Schwarzschild stars as black-hole mimickers
• Gravastars in $f(R,T,R_{\mu \nu }{T}^{\mu \nu })$ Gravity
• Wormhole Shadows in Rotating Dust
• Shadows and precession of orbits in rotating Janis-Newman-Winicour spacetime
• Wave Optics in Spacetimes with Compact Gravitating Object
• Stable and self consistent charged gravastar model within the framework of $f(R,T)$ gravity
• Thin-Shell Gravastar Model in $f(Q,T)$ Gravity
• Images of hairy Reissner-Nordström black hole illuminated by static accretions
• On the radial stability of ultra compact Schwarzschild stars beyond the Buchdahl limit
• Gravitational Vacuum Condensate Stars
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• Stable Charged Gravastar model in Cylindrically Symmetric Space-time
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• Existence and Stability of Static Spherical Fluid Shells in a Schwarzschild-Rindler-anti-de Sitter Metric
• Maximum mass of a barotropic spherical star
• Imaging a semi-classical horizonless compact object with strong redshift
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• Herrera Complexity and Shadows of Spherically Symmetric Compact Objects
• Impact of Charge on Gravastars in $f(\mathfrak{R},{\mathcal{T}}^2)$ Gravity
• Solitonic Gravastars in a U(1) gauge Higgs model
• Synchrotron emitting Komissarov torus around naked singularities
• Multiple Rings in the Shadow of Extremely Compact Objects
• Gravastar in the framework of Loop Quantum Cosmology
• Stabilizing Spherical Energy Shells with Angular Momentum in Gravitational Backgrounds
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• Exact Gravastar Solution
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