Equatorial timelike circular orbits around generic ultracompact objects

Abstract

For a stationary, axisymmetric, asymptotically flat, ultra-compact [$i.e.$ containing light-rings (LRs)] object, with a ${\mathbb{Z}}_2$ north-south symmetry fixing an equatorial plane, we establish that the structure of timelike circular orbits (TCOs) in the vicinity of the equatorial LRs, for either rotation direction, depends exclusively on the radial stability of the LRs. Thus, an unstable LR delimits a region of unstable TCOs (no TCOs) radially above (below) it; a stable LR delimits a region of stable TCOs (no TCOs) radially below (above) it. Corollaries are discussed for both horizonless ultra-compact objects and black holes. We illustrate these results with a variety of exotic stars examples and non-Kerr black holes, for which we also compute the efficiency associated with converting gravitational energy into radiation by a material particle falling under an adiabatic sequence of TCOs. For most objects studied, it is possible to obtain efficiencies larger than the maximal efficiency of Kerr black holes, $i.e.$ larger than $42\%$.

21 pages, 11 figures. Accepted in PRD

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Cited by in corpus (24)

• Topology of equatorial timelike circular orbits around stationary black holes
• Distinct topological configurations of equatorial timelike circular orbit for spherically symmetric (hairy) black holes
• Static spheres around spherically symmetric black hole spacetime
• Mutual Influence of Photon Sphere and Non-Commutative Parameter in Various Non-Commutative Black Holes: Part I- Towards evidence for WGC
• Proca-Higgs balls and stars in a UV completion for Proca self-interactions
• Extracting energy via magnetic reconnection from Kerr-de Sitter black holes
• Equatorial extreme-mass-ratio inspirals in Kerr black holes with scalar hair spacetimes
• Stability and physical properties of spherical excited scalar boson stars
• WGC as WCCC protector: The Synergistic Effects of various Parameters in Identifying WGC candidate Models
• Topology of Born-Infeld-AdS Black Hole Phase Transitions: Bulk and CFT Sides
• Mechanisms Behind the Aschenbach Effect in Non-Rotating Black Hole Spacetime
• Aschenbach effect and circular orbits in static and spherically symmetric black hole backgrounds
• Curved accretion disks around rotating black holes without reflection symmetry
• Self-interactions can (also) destabilize bosonic stars
• Static spheres and Aschenbach effect for black holes in massive gravity
• Equatorial orbits of spinning test particle in rotating boson star
• Splitting the Gravitational Atom: Instabilities of Black Holes with Synchronized or Resonant Hair
• Epicyclic Frequencies for a Generic Ultracompact Object
• Chaotic dynamics of pulsating spheres orbiting black holes
• Slowly Rotating Boson Stars
• Geodesic structure of a noncommutative black hole
• Polish Doughnuts around Scalarized Kerr Black Holes
• There and back again: Outspiraling motion in non-Kerr compact objects
• Topological charge and black hole photon spheres in massive gravity