Issue |
A&A
Volume 694, February 2025
|
|
---|---|---|
Article Number | A135 | |
Number of page(s) | 11 | |
Section | Numerical methods and codes | |
DOI | https://doi.org/10.1051/0004-6361/202452679 | |
Published online | 07 February 2025 |
Black hole accretion and radiation variability in general relativistic magnetohydrodynamic simulations with Rezzolla–Zhidenko spacetime
1
Instituto de Astrofísica de Andalucía-CSIC, Glorieta de la Astronomía s/n,
18008
Granada,
Spain
2
Institut für Theoretische Physik, Goethe-Universität Frankfurt,
Max-von-Laue-Strasse 1,
60438
Frankfurt am Main,
Germany
3
Mizusawa VLBI Observatory, National Astronomical Observatory of Japan,
2-12 Hoshigaoka, Mizusawa, Oshu,
Iwate
023-0861,
Japan
4
Instituto de Astronomía, Universidad Nacional Autónoma de México,
AP 70-264,
Ciudad de México
04510,
Mexico
5
Tsung-Dao Lee Institute, Shanghai Jiao Tong University,
No.1 Lisuo Road,
Shanghai
201210,
PR China
6
School of Physics and Astronomy, Shanghai Jiao Tong University,
800 Dongchuan Road,
Shanghai
200240,
PR China
★ Corresponding authors; moriyama@iaa.es; aosorio@astro.unam.mx
Received:
20
October
2024
Accepted:
10
January
2025
The Event Horizon Telescope (EHT) has unveiled the horizon-scale radiation properties of Sagittarius A* (Sgr A*), the supermassive black hole at the center of our galaxy, providing a novel platform for testing gravitational theories by comparing observations with theoretical models. A key next step is to investigate the nature of accretion flows and spacetime structures near black holes by analyzing the time variability observed in EHT data alongside general relativistic magnetohydrodynamic (GRMHD) simulations. We explored the dynamics of accretion flows in spherically symmetric black hole spacetimes with deviations from general relativity utilizing two dimensional GRMHD simulations based on the Rezzolla–Zhidenko parameterized spacetime. This study marks the first systematic investigation into how variability amplitudes in light curves, derived from non-Kerr GRMHD simulations, depend on deviations from the Schwarzschild spacetime. The deviation parameters are consistent with the constraints from weak gravitational fields and the size of Sgr A*’s black hole shadow. We find that the dynamics of accretion flows systematically depend on these parameters. In spacetimes with a deeper gravitational potential, fluid and Alfvén velocities consistently decrease relative to the Schwarzschild metric, indicating weaker dynamical behavior. We also examined the influence of spacetime deviations on radiation properties by computing luminosity fluctuations at 230 GHz using general relativistic radiative transfer simulations, in line with EHT observations. The amplitude of these fluctuations exhibits a systematic dependence on the deviation parameters, decreasing for deeper gravitational potentials compared to the Schwarzschild metric. These features are validated using one of the theoretically predicted metrics, the Hayward metric, a model that describes nonsingular black holes. This characteristic is expected to have similar effects in more comprehensive simulations that include more realistic accretion disk models and electron cooling in the future, potentially aiding in distinguishing black hole solutions that explain the variability of Sgr A*.
Key words: black hole physics / gravitation / hydrodynamics / magnetohydrodynamics (MHD) / radiative transfer
© The Authors 2025
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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