Thin Accretion Disks around Rotating Charged Black Holes in an Effective Higher-Curvature Spacetime

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Main Authors: Hassani, Mohammad, Nozari, Kourosh, Saghafi, Sara
Format: Preprint
Published: 2026
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author Hassani, Mohammad
Nozari, Kourosh
Saghafi, Sara
author_facet Hassani, Mohammad
Nozari, Kourosh
Saghafi, Sara
contents We investigate the structure and emission properties of a thin accretion disk around a rotating charged black hole described by an effective higher-curvature-inspired spacetime, constructed as a phenomenological deformation of the Kerr Newman geometry. In this framework, the deformation is introduced through a modification of the metric function $Δ$ by an effective Gauss-Bonnet-like parameter $α$, such that the spacetime reduces to the standard Kerr Newman solution in the limit $α\to 0$. Adopting a kinematical approach, we use test-particle motion to derive the specific energy, specific angular momentum, and angular velocity of circular orbits, and analyze the effects of the parameters $α$ and charge $Q$ on the innermost stable circular orbit (ISCO), radiative efficiency, radiation flux, temperature, and differential luminosity of the disk. We find that increasing $α$ shifts the ISCO inward and enhances the disk's radiation flux and temperature, while the presence of charge suppresses these quantities due to electrostatic effects. Our results demonstrate that effective higher curvature deformations of rotating black hole spacetimes can lead to observable deviations from the Kerr case, highlighting accretion disks as sensitive probes of strong-gravity effects without relying on a specific underlying gravitational theory.
format Preprint
id arxiv_https___arxiv_org_abs_2605_13797
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Thin Accretion Disks around Rotating Charged Black Holes in an Effective Higher-Curvature Spacetime
Hassani, Mohammad
Nozari, Kourosh
Saghafi, Sara
General Relativity and Quantum Cosmology
Cosmology and Nongalactic Astrophysics
High Energy Physics - Phenomenology
High Energy Physics - Theory
We investigate the structure and emission properties of a thin accretion disk around a rotating charged black hole described by an effective higher-curvature-inspired spacetime, constructed as a phenomenological deformation of the Kerr Newman geometry. In this framework, the deformation is introduced through a modification of the metric function $Δ$ by an effective Gauss-Bonnet-like parameter $α$, such that the spacetime reduces to the standard Kerr Newman solution in the limit $α\to 0$. Adopting a kinematical approach, we use test-particle motion to derive the specific energy, specific angular momentum, and angular velocity of circular orbits, and analyze the effects of the parameters $α$ and charge $Q$ on the innermost stable circular orbit (ISCO), radiative efficiency, radiation flux, temperature, and differential luminosity of the disk. We find that increasing $α$ shifts the ISCO inward and enhances the disk's radiation flux and temperature, while the presence of charge suppresses these quantities due to electrostatic effects. Our results demonstrate that effective higher curvature deformations of rotating black hole spacetimes can lead to observable deviations from the Kerr case, highlighting accretion disks as sensitive probes of strong-gravity effects without relying on a specific underlying gravitational theory.
title Thin Accretion Disks around Rotating Charged Black Holes in an Effective Higher-Curvature Spacetime
topic General Relativity and Quantum Cosmology
Cosmology and Nongalactic Astrophysics
High Energy Physics - Phenomenology
High Energy Physics - Theory
url https://arxiv.org/abs/2605.13797