Observational signatures of Bardeen black holes under nonlinear electrodynamics
Abstract
We investigate the shadow and optical appearance of the Bardeen black hole (BH) within nonlinear electrodynamics (NLED). Since photon propagation in nonlinear electromagnetic field can be equivalently described as null-geodesic motion in the effective metric induced by NLED, we derive the corresponding effective optical geometry of the NLED-Bardeen BH. Furthermore, by examining the horizon-photon sphere-shadow inequality, we demonstrate that the NLED-Bardeen BH does not satisfy the complete inequality chain. In addition, we investigate photon dynamics and the corresponding optical images generated by both thin disk and spherical accretion models. Increasing g/M reduces the photon sphere radius and critical impact parameter, resulting in a more compact shadow and an inward shift of the emission peak. For the thin disk accretion model, photon trajectories are classified into direct emission, lensing ring, and photon ring components according to the corresponding impact parameter. We find that Model 1 exhibits three distinct intensity peaks, whereas Models 2 and 3 display two and one peaks. The systematic dependence of these features on the magnetic charge indicates that the NLED-Bardeen BH may exhibit observational signatures distinguishable from those of the Bardeen BH. In static spherical accretion, the intensity peaks near the critical impact parameter because of the enhanced optical path length, while infalling spherical accretion introduces an additional Doppler redshift that suppresses the observed intensity. These results indicate that the shadow size, ring structure, and intensity distribution can serve as potential observational signatures of NLED effects in the strong-field regime.
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BibTeX
@misc{feng2026observational,
title = {{Observational signatures of Bardeen black holes under nonlinear electrodynamics}},
author = {Haiyuan Feng and Dan-Dan Cui},
howpublished = {arXiv},
year = {2026},
month = nov,
doi = {10.48550/arxiv.2611.09979},
eprint = {2611.09979},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2611.09979},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Observational signatures of Bardeen black holes under nonlinear electrodynamics
AU - Haiyuan Feng
AU - Dan-Dan Cui
PY - 2026
DA - 2026/11/01
PB - arXiv
DO - 10.48550/arxiv.2611.09979
UR - https://arxiv.org/abs/2611.09979
AB - We investigate the shadow and optical appearance of the Bardeen black hole (BH) within nonlinear electrodynamics (NLED). Since photon propagation in nonlinear electromagnetic field can be equivalently described as null-geodesic motion in the effective metric induced by NLED, we derive the corresponding effective optical geometry of the NLED-Bardeen BH. Furthermore, by examining the horizon-photon sphere-shadow inequality, we demonstrate that the NLED-Bardeen BH does not satisfy the complete inequality chain. In addition, we investigate photon dynamics and the corresponding optical images generated by both thin disk and spherical accretion models. Increasing g/M reduces the photon sphere radius and critical impact parameter, resulting in a more compact shadow and an inward shift of the emission peak. For the thin disk accretion model, photon trajectories are classified into direct emission, lensing ring, and photon ring components according to the corresponding impact parameter. We find that Model 1 exhibits three distinct intensity peaks, whereas Models 2 and 3 display two and one peaks. The systematic dependence of these features on the magnetic charge indicates that the NLED-Bardeen BH may exhibit observational signatures distinguishable from those of the Bardeen BH. In static spherical accretion, the intensity peaks near the critical impact parameter because of the enhanced optical path length, while infalling spherical accretion introduces an additional Doppler redshift that suppresses the observed intensity. These results indicate that the shadow size, ring structure, and intensity distribution can serve as potential observational signatures of NLED effects in the strong-field regime.
ER -