Black hole mimicker hiding in the shadow: Optical properties of the $\gamma$-metric

Abstract

Can the observation of the "shadow" allow us to distinguish a black hole from a more exotic compact object? We study the motion of photons in a class of vacuum static axially-symmetric space-times that is continuously linked to the Schwarzschild metric through the value of one parameter that can be interpreted as a measure of the deformation of the source. We investigate the lensing effect and shadow produced by the source with the aim of comparing the expected image with the shadow of a Schwarzschild black hole. In the context of astrophysical black holes we found that it may not be possible to distinguish an exotic source with small deformation parameter from a black hole. However, as the deformation increases noticeable effects arise. Therefore, the future more precise measurement of the shadow of astrophysical black hole candidates would in principle allow to put constraints on the deviation of the object from spherical symmetry.

12 pages, 7 figures. v3: refereed version

References in corpus (19)

• First M87 Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole
• First M87 Event Horizon Telescope Results. VI. The Shadow and Mass of the Central Black Hole
• Measurement of the Kerr Spin Parameter by Observation of a Compact Object's Shadow
• A Metric for Rapidly Spinning Black Holes Suitable for Strong-Field Tests of the No-Hair Theorem
• Tests for the existence of horizons through gravitational wave echoes
• A new method for shadow calculations: application to parameterised axisymmetric black holes
• Apparent shape of super-spinning black holes
• Null geodesics and shadow of a rotating black hole in extended Chern-Simons modified gravity
• Shadow of a Kaluza-Klein rotating dilaton black hole
• Testing the black hole "no-hair" hypothesis
• The effect of the Brane-Dicke coupling parameter on weak gravitational lensing by wormholes and naked singularities
• Gravitational Lensing in presence of Plasma: Strong Lens Systems, Black Hole Lensing and Shadow
• Shape and position of the shadow in the $\delta =2$ Tomimatsu-Sato space-time
• Profiles of emission lines generated by rings orbiting braneworld Kerr black holes
• Understanding photon sphere and black hole shadow in dynamically evolving spacetimes
• Shadows of CPR black holes and tests of the Kerr metric
• Constraints on the spacetime metric around seven "bare" AGNs using X-ray reflection spectroscopy
• Imaging black holes: past, present and future
• The Erez-Rosen metric and the role of the quadrupole on light propagation