Stable photon orbits in stationary axisymmetric electrovacuum spacetimes

Dolan, Sam R.; Shipley, Jake O.

doi:10.1103/physrevd.94.044038

Cited by 30 publications

(27 citation statements)

References 62 publications

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“…Above the minimum, the bounded light orbits with two radial turning points are located. Their existence serves an indication that the solution may be unstable [17][18][19][20]. Stable photon rings are often encountered near (hypothetical) horizonless ultra-compact objects, thus indicating on their instability [21].…”

Section: Introductionmentioning

confidence: 99%

Completing characterization of photon orbits in Kerr and Kerr-Newman metrics

Gal’tsov

Kobialko

2019

Phys. Rev. D

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Recently, several new characteristics have been introduced to describe null geodesic structure of stationary spacetimes, such as photon regions (PR) and transversely trapping surfaces (TTS). The former are three-dimensional domains confining the spherical photon orbits, while the latter are closed twosurface of spherical topology which fill other regions called TTR. It is argued that in generic stationary axisymmetric spacetime it is natural to consider also the non-closed TTSs of the geometry of spherical cups, satisfying the same conditions ("partial" TTS or PTTS), which fill the three-dimensional regions, PTTR. We then show that PR, TTR and PTTR together with the corresponding anti-trapping regions constitute the complete set of regions filling the entire three-space (where timelike surfaces are defined) of Kerr-like spacetimes. This construction provides a novel optical description of such spacetimes without recurring to explicit solution of the geodesic equations. Applying this analysis to Kerr-Newman metrics (including the overspinning ones) we reveal four different optical types for different sets of the rotation and charge parameters. To illustrate their properties we extend Synge analysis of photon escape in the Schwarzschild metric to stationary spacetimes and construct density graphs describing escape of photons from all the above regions.

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Section: Introductionmentioning

confidence: 99%

Completing characterization of photon orbits in Kerr and Kerr-Newman metrics

Gal’tsov

Kobialko

2019

Phys. Rev. D

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“…Thus, the equipotential lines of h AE ðr; θÞ give the boundary of the allowed region in the ðr; θÞ-space, for each value of η. A similar effective potential was recently used in [45,46]. Moreover, since the solutions of the quadratic equation are In the limit g tt → 0, one of the functions h AE diverges and the other converges toh.…”

Section: B the Two 2d Effective Potentialsmentioning

confidence: 99%

“…1. Chaotic scattering in GR spacetimes has been observed and discussed in binary or multi-BH solutions (see, e.g., [45,46,[74][75][76][77][78][79][80][81][82][83][84]) and is well known in the context of manybody scattering in classical dynamics, for example, the scattering of charged particles off magnetic dipoles [85] and the three-body problem (see, e.g., [86]). KBHsSH or RBSs provide an example of chaos in geodesic motion on the background of a single compact object, which moreover solves a simple and well-defined matter model minimally coupled to GR.…”

Section: Introductionmentioning

confidence: 99%

Chaotic lensing around boson stars and Kerr black holes with scalar hair

et al. 2016

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In a recent paper [P. V. P. Cunha, C. A. R. Herdeiro, E. Radu, and H. F. Runarsson, Phys. Rev. Lett. 115, 211102 (2015).], it was shown that the lensing of light around rotating boson stars and Kerr black holes with scalar hair can exhibit chaotic patterns. Since no separation of variables is known (or expected) for geodesic motion on these backgrounds, we examine the 2D effective potentials for photon trajectories, to obtain a deeper understanding of this phenomenon. We find that the emergence of stable light rings on the background spacetimes allows the formation of "pockets" in one of the effective potentials, for open sets of impact parameters, leading to an effective trapping of some trajectories, dubbed "quasibound orbits." We conclude that pocket formation induces chaotic scattering, although not all chaotic orbits are associated to pockets. These and other features are illustrated in a gallery of examples, obtained with a new ray-tracing code, PYHOLE, which includes tools for a simple, simultaneous visualization of the effective potential, together with the spacetime trajectory, for any given point in a lensing image. An analysis of photon orbits allows us to further establish a positive correlation between photon orbits in chaotic regions and those with more than one turning point in the radial direction; we recall that the latter is not possible around Kerr black holes. Moreover, we observe that the existence of several light rings around a horizon (several fundamental orbits, including a stable one), is a central ingredient for the existence of multiple shadows of a single hairy black hole. We also exhibit the lensing and shadows by Kerr black holes with scalar hair, observed away from the equatorial plane, obtained with PYHOLE.

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“…In addition, h 0 (ρ, 0) also vanishes for g = 0, which is similar to the behavior seen in Eqs. (25) and (26). This fact implies that the monotonicity of angular momentum and energy for a circular orbit switches at zeros of h 0 (ρ, 0).…”

Section: Stability Conditions Of Circular Orbits In the Majumdar-mentioning

confidence: 93%

Innermost stable circular orbits in the Majumdar-Papapetrou dihole spacetime

Nakashi

Igata

2019

Phys. Rev. D

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We investigate the positions of stable circular massive particle orbits in the Majumdar-Papapetrou dihole spacetime with equal mass. In terms of qualitative differences of their sequences, we classify the dihole separation into five ranges and find four critical values as the boundaries. When the separation is relatively large, the sequence on the symmetric plane bifurcates, and furthermore, they extend to each innermost stable circular orbit in the vicinity of each black hole. In a certain separation range, the sequence on the symmetric plane separates into two parts. On the basis of this phenomenon, we discuss the formation of double accretion disks with a common center. Finally, we clarify the dependence of the radii of marginally stable circular orbits and innermost stable circular orbits on the separation parameter. We find a discontinuous transition of the innermost stable circular orbit radius. We also find the separation range at which the radius of the innermost stable circular orbit can be smaller than that of the stable circular photon orbit. * Electronic address: nakashi@rikkyo.ac.jp † Electronic address: igata@rikkyo.ac.jp

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Stable photon orbits in stationary axisymmetric electrovacuum spacetimes

Cited by 30 publications

References 62 publications

Completing characterization of photon orbits in Kerr and Kerr-Newman metrics

Completing characterization of photon orbits in Kerr and Kerr-Newman metrics

Chaotic lensing around boson stars and Kerr black holes with scalar hair

Innermost stable circular orbits in the Majumdar-Papapetrou dihole spacetime

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