Two shadows of a single black hole: Vacuum birefringence phenomena within Einstein-nonlinear-electrodynamics

Abstract

One of the main features of nonlinear electrodynamics is the existence of an effective geometry that describes the geodesic motion of photons. A detailed analysis of the properties of effective geometry is of utmost importance for a better understanding of nonlinear electrodynamics theories and their possible imprints on physics, especially in the context of black holes. We consider a nonlinear electrodynamics model that depends on the two electromagnetic scalar invariants and obtain that the motion of photons in nonlinear electrodynamics exhibits \textit{vacuum birefringence}, i.e., photons can propagate along two distinct paths, depending on their polarization. As a consequence of this phenomenon, we show that static black hole solutions sourced by nonlinear electrodynamics can admit two distinct unstable light rings, leading to the formation of two distinct shadows. Moreover, to explore the potential astrophysical relevance of our results, we also compare them with the astrophysical observations for the shadow radius of Sagittarius A*. We place upper limits on the charge-to-mass ratio of the nonlinear electrodynamics-sourced black hole. We also show that the motion of photons in this context can be interpreted as nongeodesic curves subjected to a four-force term from the perspective of an observer in the spacetime metric, generalizing previous results in the literature for nonlinear electrodynamics models that depend on a single electromagnetic scalar invariant.

21 pages, 15 figures. To match published version

References in corpus (26)

• First M87 Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole
• First Sagittarius A* Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole in the Center of the Milky Way
• Horizon-scale tests of gravity theories and fundamental physics from the Event Horizon Telescope image of Sagittarius A${}^{\ast }$
• Detection of the Schwarzschild precession in the orbit of the star S2 near the Galactic centre massive black hole
• Advances in QED with intense background fields
• Regular black holes with a nonlinear electrodynamics source
• Applications of the Gauss-Bonnet theorem to gravitational lensing
• Magnetically charged black holes from non-linear electrodynamics and the Event Horizon Telescope
• Gravitational Lensing by Rotating Wormholes
• Chaotic lensing around boson stars and Kerr black holes with scalar hair
• Evidence for vacuum birefringence from the first optical polarimetry measurement of the isolated neutron star RX\, J1856.5$-$3754
• Introductory Notes on Non-linear Electrodynamics and its Applications
• Weak gravitational lensing of regular black holes with cosmic strings using the Gauss-Bonnet theorem
• QED Effect on Black Hole Shadow
• What does a binary black hole merger look like?
• Polarimetry and Astrometry of NIR Flares as Event Horizon Scale, Dynamical Probes for the Mass of Sgr A*
• Effect of Non-linear Electrodynamics on Weak field deflection angle by Black Hole
• Quasinormal modes of charged black holes with corrections from nonlinear electrodynamics
• Regular Black Holes: Towards a New Paradigm of Gravitational Collapse
• Particle motion around generic black holes coupled to non-linear electrodynamics
• Birefringence and QuasiNormal Modes of the Einstein-Euler-Heisenberg Black Hole
• Can a light ray distinguish charge of a black hole in nonlinear electrodynamics?
• Light rings and causality for nonsingular ultracompact objects sourced by nonlinear electrodynamics
• Geodesic of nonlinear electrodynamics and stable photon orbits
• Generalized Gibbons-Werner method for stationary spacetimes
• Good tachyons, bad bradyons: role reversal in Einstein-nonlinear-electrodynamics models