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Polarized Radiative Transfer of Kerr-Newman Black Hole

Xin Li, Guo Sen, Pei Wang, En-Wei Liang, Xiao-Xiong Zeng, Kai Lin

Abstract

In this analysis, we investigate the polarization radiation imaging of Kerr-Newman black holes, with a particular focus on the impact of black hole charge on photon propagation and polarization characteristics. By extending the traditional Walker-Penrose method, which is limited by its reliance on specific symmetric structures and Killing tensors, we overcome these limitations by constructing an ordinary differential equations (ODEs) numerical framework that combines the photon orbit equation with the polarization parallel transport equation. This allows for the self-consistent evolution of photon trajectories and polarization states in any spacetime backgrounds without relying on specific symmetries. Using this framework, we analyze the effects of black hole spin and charge on the polarization characteristics of radiation from both prograde and retrograde accretion disks. Our results show that black hole charge can significantly modify photon trajectories and polarization patterns: increasing charge compresses and distorts the EVPA structure on photon-ring scales, inducing localized rotations and asymmetries that may provide a potential diagnostic of a nonzero black hole charge.

Polarized Radiative Transfer of Kerr-Newman Black Hole

Abstract

In this analysis, we investigate the polarization radiation imaging of Kerr-Newman black holes, with a particular focus on the impact of black hole charge on photon propagation and polarization characteristics. By extending the traditional Walker-Penrose method, which is limited by its reliance on specific symmetric structures and Killing tensors, we overcome these limitations by constructing an ordinary differential equations (ODEs) numerical framework that combines the photon orbit equation with the polarization parallel transport equation. This allows for the self-consistent evolution of photon trajectories and polarization states in any spacetime backgrounds without relying on specific symmetries. Using this framework, we analyze the effects of black hole spin and charge on the polarization characteristics of radiation from both prograde and retrograde accretion disks. Our results show that black hole charge can significantly modify photon trajectories and polarization patterns: increasing charge compresses and distorts the EVPA structure on photon-ring scales, inducing localized rotations and asymmetries that may provide a potential diagnostic of a nonzero black hole charge.
Paper Structure (5 sections, 25 equations, 15 figures)

This paper contains 5 sections, 25 equations, 15 figures.

Table of Contents

  1. Introduction
  2. ODE equations for photon dynamics and polarization transport in Kerr-Newman spacetime
  3. Initial conditions for solving the ODE in Kerr-Newman spacetime
  4. Solving the ODE and image simulation
  5. Conclusion and Discussion

Figures (15)

  • Figure 1: Four-component projection method from Ref. Zhao:2025nwi.
  • Figure 2: Intensity distribution of Gaussian model. The change of parameter $\beta$ only adjusts the position where the peak appears.
  • Figure 3: Intensity profiles of the non-Gaussian radiation models. The variation of parameter $\gamma$ can regulate the asymmetry of the accretion disk structure.
  • Figure 4: Polarized emission profiles for this model.
  • Figure 5: Generalized polarized emission profiles under varying parameters.
  • ...and 10 more figures