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arxiv 0904.3575 v3 pith:ZBED45TO submitted 2009-04-23 astro-ph.HE gr-qc

Measurement of the Kerr Spin Parameter by Observation of a Compact Object's Shadow

classification astro-ph.HE gr-qc
keywords parameterkerrshadowspinangleapparentblackhole
verification ladder T0 review T1 audit T2 compute T3 formal T4 reserved
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A black hole casts a shadow as an optical appearance because of its strong gravitational field. We study how to determine the spin parameter and the inclination angle by observing the apparent shape of the shadow, which is distorted mainly by those two parameters. Defining some observables characterizing the apparent shape (its radius and distortion parameter), we find that the spin parameter and inclination angle of a Kerr black hole can be determined by the observation. This technique is also extended to the case of a Kerr naked singularity.

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Cited by 11 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score.

  1. Determining Kerr black hole spin and inclination from a segment of the critical curve in black hole images

    gr-qc 2026-06 unverdicted novelty 7.0

    Three observables on a standardized segment of the Kerr critical curve uniquely fix spin a/M, inclination i, and segment location r_nl within the considered domain.

  2. Constitutive birefringence and critical curves in the rotating Garc\'ia--D\'iaz black hole

    gr-qc 2026-06 unverdicted novelty 7.0

    In the rotating García-Díaz NLED black hole the Fresnel quartic factorizes into two optical metrics whose critical families project to distinct contours Γ+ and Γ- whose angular separation is generated by the constitut...

  3. Strong-deflection expansion of the deflection angle near a degenerate photon sphere

    gr-qc 2026-03 unverdicted novelty 7.0

    Derives a factorized leading term for the strong deflection angle near degenerate photon spheres using local expansion of the effective potential and Weyl tensor measures.

  4. Rotating Black Holes with Primary Scalar Hair: Shadow Signatures in Beyond Horndeski Gravity

    gr-qc 2026-02 unverdicted novelty 7.0

    Rotating black holes with primary scalar hair in beyond Horndeski gravity produce shadows whose diameter increases for negative Q and whose distortion increases for positive Q, with EHT bounds on M87* restricting but ...

  5. Topological charge and black hole photon spheres in massive gravity

    gr-qc 2025-09 unverdicted novelty 7.0

    In dRGT massive gravity, static spherically symmetric black holes exhibit zero, one, or two photon spheres whose topological charges and stability patterns differ from Einstein gravity and from horizonless compact objects.

  6. Gravity/thermodynamics correspondence via black hole shadows

    gr-qc 2026-04 unverdicted novelty 6.0

    Cuspy black hole shadows correspond to swallowtail thermodynamic free energy, with boundary self-intersections marking geometric phase transitions whose critical exponents fall in the mean-field class.

  7. From Ringdown to Lensing: Analytic Eikonal Modes of Quasi-Topological Regular Black Holes

    gr-qc 2026-04 unverdicted novelty 5.0

    Analytic quasinormal-mode expressions and explicit QNM-shadow-lensing correspondence for four-dimensional quasi-topological regular black holes.

  8. Quasi-resonances in the vicinity of Einstein-Maxwell-dilaton black hole

    gr-qc 2026-04 unverdicted novelty 5.0

    Increasing the mass of a perturbing scalar field around Einstein-Maxwell-dilaton black holes strongly suppresses damping in several quasinormal branches, producing quasi-resonant long-lived oscillations.

  9. A First-Order Eikonal Framework for Quasinormal Modes, Shadows, Strong Lensing, and Grey-Body Factors in a Scalarized Black-Hole Metric

    gr-qc 2026-04 unverdicted novelty 4.0

    Derives closed first-order eikonal expressions that connect a scalarized black-hole metric to quasinormal frequencies, shadows, strong deflection, and transmission probabilities.

  10. A First-Order Eikonal Framework for Quasinormal Modes, Shadows, Strong Lensing, and Grey-Body Factors in a Scalarized Black-Hole Metric

    gr-qc 2026-04 unverdicted novelty 4.0

    First-order eikonal formulas connect a scalarized black-hole metric to quasinormal modes, shadows, strong lensing, and grey-body factors via photon-sphere invariants in the weak-hair limit.

  11. Probing Kalb-Ramond gravity with charged rotating black holes: constraints from EHT observations

    gr-qc 2026-04 unverdicted novelty 3.0

    EHT shadow observations constrain the Lorentz-violating parameter ℓ in Kalb-Ramond gravity for charged rotating black holes to roughly |ℓ| ≲ 0.1-0.2, with an upper bound ℓ ≲ 0.19 from Sgr A*.