Radiative Efficiency Enhancement by Electromagnetic Energy Dissipation in Strongly Magnetized Supercritical Accretion Flows around Kerr Black Holes
Abstract
We investigate how black hole spin and the amount of magnetic flux affect electromagnetic energy dissipation and radiation transport in supercritical accretion flows. For this purpose, we perform general relativistic radiation magnetohydrodynamic simulations of MAD and SANE accretion flows with different black hole spins. In the high-spin MAD model, we find that a fraction of the electromagnetic energy extracted by the Blandford--Znajek mechanism is dissipated near the disk surface in the vicinity of the black hole. This dissipation significantly contributes to the generation of radiative energy and enhances the luminosity. The time-averaged radiative efficiency reaches ηrad=0.60, which is much larger than $0.088$ for the non-spinning black hole case and $0.21$ for the weak-magnetic-flux case, corresponding to the SANE state. As a result, the effective trapping radius, defined as the radius at which the outward radiative luminosity becomes equal to the inward radiative luminosity, is rtrap=2.5rg, comparable to the ISCO radius. This value is significantly smaller than 12rg for the non-spinning case and 8.5rg for the SANE state. These results suggest that the amount of magnetic flux accumulated on the black hole can affect the radiative properties of supercritical accretion flows and should therefore be considered, in addition to black hole mass, spin, and mass accretion rate, when interpreting observed luminosities and spectra.
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BibTeX
@misc{takahashi2026radiative,
title = {{Radiative Efficiency Enhancement by Electromagnetic Energy Dissipation in Strongly Magnetized Supercritical Accretion Flows around Kerr Black Holes}},
author = {Hiroyuki R. Takahashi and Ken Ohsuga and Ryohei Kobayashi and Akihiro Inoue and Yuta Asahina and Akira Nukada and Taisuke Boku},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.03250},
eprint = {2609.03250},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.03250},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Radiative Efficiency Enhancement by Electromagnetic Energy Dissipation in Strongly Magnetized Supercritical Accretion Flows around Kerr Black Holes
AU - Hiroyuki R. Takahashi
AU - Ken Ohsuga
AU - Ryohei Kobayashi
AU - Akihiro Inoue
AU - Yuta Asahina
AU - Akira Nukada
AU - Taisuke Boku
PY - 2026
DA - 2026/09/03
PB - arXiv
DO - 10.48550/arxiv.2609.03250
UR - https://arxiv.org/abs/2609.03250
AB - We investigate how black hole spin and the amount of magnetic flux affect electromagnetic energy dissipation and radiation transport in supercritical accretion flows. For this purpose, we perform general relativistic radiation magnetohydrodynamic simulations of MAD and SANE accretion flows with different black hole spins. In the high-spin MAD model, we find that a fraction of the electromagnetic energy extracted by the Blandford--Znajek mechanism is dissipated near the disk surface in the vicinity of the black hole. This dissipation significantly contributes to the generation of radiative energy and enhances the luminosity. The time-averaged radiative efficiency reaches η_rad=0.60, which is much larger than $0.088$ for the non-spinning black hole case and $0.21$ for the weak-magnetic-flux case, corresponding to the SANE state. As a result, the effective trapping radius, defined as the radius at which the outward radiative luminosity becomes equal to the inward radiative luminosity, is r_trap=2.5r_g, comparable to the ISCO radius. This value is significantly smaller than 12r_g for the non-spinning case and 8.5r_g for the SANE state. These results suggest that the amount of magnetic flux accumulated on the black hole can affect the radiative properties of supercritical accretion flows and should therefore be considered, in addition to black hole mass, spin, and mass accretion rate, when interpreting observed luminosities and spectra.
ER -