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Parameter estimation of hairy Kerr black holes from its shadow and constraints from M87*

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arxiv 2103.11417 v3 pith:KZM67XR2 submitted 2021-03-21 gr-qc astro-ph.GAhep-th

classification gr-qcastro-ph.GAhep-th
keywords blackholeskerrhairyholeshadowalphashadows
verification ladder T0 review T1 audit T2 compute T3 formal
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abstract

The recently obtained hairy Kerr black holes, due to additional sources or surrounding fluid, like dark matter, with conserved energy-momentum tensor, have a deviation $\alpha$ and primary hair $l_0$, apart from rotation parameter $a$ and mass $M$. In the wake of the \textit{Event Horizon Telescope} (\textit{EHT}) observations of the supermassive black hole M87*, a recent surge in interest in black hole shadows suggests comparing the black holes in general relativity (GR) and modified theories of gravity (MoG) to assess these models' differences. Motivated by this, we take on an extensive study of the rotating hairy Kerr black holes, which encompasses, in particular cases, the Kerr black hole ($\alpha=0$). We investigate ergosphere and shadows of the black holes to infer that their size and shape are affected due to the $l_0$ and are found to harbour a richer chaotic structure. In particular, the hairy Kerr black holes possess smaller size but more distorted shadows when compared with Kerr black holes. We also estimate the parameters $l_0$ and $a$ associated with hairy Kerr black holes using the shadow observables. The inferred circularity deviation $\Delta C \leq 0.1$ for the M87* black hole is satisfied, whereas shadow angular diameter $\theta_{d}=42 \pm 3 \mu as$, within $1 \sigma$ region, for a given choice of $\alpha$, places bounds on the parameters $a$ and $l_0$. Interestingly, the shadow axial ratio obeying $1< D_x \lesssim 4/3$ is in agreement with the \textit{EHT} results and thus eventuates in the hairy Kerr black holes being suitable candidates for astrophysical black holes.

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Cited by 6 Pith papers

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

  1. Kerr black holes without primary hairs

    gr-qc 2026-07 conditional novelty 6.0 of 10

    Explicit infinite family of axisymmetric black holes with a Kerr exterior, a regular or mildly singular interior controlled by free exponents n_i, and no additional asymptotic charges.

  2. Constraints and Consistency of Rotating Regular Black Hole Thermodynamics

    gr-qc 2026-01 reject novelty 6.0 of 10

    For rotating regular black holes, the thermodynamic Hawking temperature is order-dependent under the regularity constraint; only computing in the full phase space before imposing the constraint reproduces the geometri...

  3. Optical Characteristics of the Kerr-Bertotti-Robinson Black Hole

    gr-qc 2025-08 conditional novelty 6.0 of 10

    For the Kerr-Bertotti-Robinson black hole, the magnetic field mainly enlarges the shadow and Einstein ring while rotation mainly distorts the shadow shape, and current M87* and Sgr A* data give only weak bounds on the field.

  4. Shadow of the generalized Vaidya black hole

    gr-qc 2026-07 conditional novelty 5.0 of 10

    For self-similar Husain black holes, the barotropic index α controls the shadow: α<1/2 enlarges it, α>1/2 shrinks it, with a quasistatic influx criterion for the time-dependent case.

  5. The shadow and quasinormal modes of the asymptotically flat hairy black holes with a dilaton potential

    gr-qc 2025-08 conditional novelty 5.0 of 10

    For exact asymptotically flat hairy charged black holes with a dilaton potential, the shadow radius, photon-orbit Lyapunov exponent, and scalar quasinormal frequencies are computed, showing strong coupling dependence ...

  6. Thermodynamics and Shadows of Kerr black holes endowed with a global monopole charge

    gr-qc 2025-06 reject novelty 4.0 of 10

    The authors derive shadow and thermodynamic quantities for a Kerr-like metric with a global monopole term in Δ, and claim EHT observations constrain the monopole charge α.

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