Modeling MAD Sgr A* flares and their dependence on spin
Abstract
Aims: This study aims to place constraints on the spin of Sgr A* from recent flare observations. It models the flare kinematics in the vicinity of a supermassive black hole, evaluates their dependence on black hole spin, and assesses the correlation between the spin of the black hole and the astrometric observations in the Galactic center. Methods: Our study extends the work of Antonopoulou et al. 2025 to a range of black hole spins. A prominent flux eruption is identified in the simulation, and the evolution of the active region on the equatorial plane is tracked during the event. The flare model consists of a spherical hot spot ejected along the flux tube with a relativistic velocity. Results: In MAD simulations, the flux tube wraps around the jet funnel in the opposite direction to the black hole's spin. This dependence is imprinted on the flare trajectory and provides a strong correlation between the spin of the black and the flare kinematics. This analysis favors Kerr black holes, with a preference towards larger spin magnitude. Although prograde simulations show a consistent clockwise motion in the sky regardless of disk rotation, retrograde models require a clockwise accretion disk to account for the observations of July 22, 2018. Conclusions: A maximally rotating Kerr black hole is the most promising candidate for reproducing the observed flare trajectory in the vicinity of Sgr A*, illustrating a pass faction surpassing 90% among the investigated flare models. In particular, determining spin orientation within this model is linked to the rotation of the accretion disk. Assuming a counterclockwise accretion disk, a prograde black hole with a≥1/2 is able to reproduce the observed flare kinematics in the Galactic center. Conversely, assuming a clockwise rotation for the disk, the observations support both prograde and retrograde Kerr black holes with a large spin.
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BibTeX
@misc{antonopoulou2026modeling,
title = {{Modeling MAD Sgr A* flares and their dependence on spin}},
author = {Eleni Antonopoulou and Antonios Nathanail and Yosuke Mizuno and Foivos Zanias},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.30095},
eprint = {2610.30095},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.30095},
}
RIS
TY - UNPB
TI - Modeling MAD Sgr A* flares and their dependence on spin
AU - Eleni Antonopoulou
AU - Antonios Nathanail
AU - Yosuke Mizuno
AU - Foivos Zanias
PY - 2026
DA - 2026/10/21
PB - arXiv
DO - 10.48550/arxiv.2610.30095
UR - https://arxiv.org/abs/2610.30095
AB - Aims: This study aims to place constraints on the spin of Sgr A* from recent flare observations. It models the flare kinematics in the vicinity of a supermassive black hole, evaluates their dependence on black hole spin, and assesses the correlation between the spin of the black hole and the astrometric observations in the Galactic center. Methods: Our study extends the work of Antonopoulou et al. 2025 to a range of black hole spins. A prominent flux eruption is identified in the simulation, and the evolution of the active region on the equatorial plane is tracked during the event. The flare model consists of a spherical hot spot ejected along the flux tube with a relativistic velocity. Results: In MAD simulations, the flux tube wraps around the jet funnel in the opposite direction to the black hole's spin. This dependence is imprinted on the flare trajectory and provides a strong correlation between the spin of the black and the flare kinematics. This analysis favors Kerr black holes, with a preference towards larger spin magnitude. Although prograde simulations show a consistent clockwise motion in the sky regardless of disk rotation, retrograde models require a clockwise accretion disk to account for the observations of July 22, 2018. Conclusions: A maximally rotating Kerr black hole is the most promising candidate for reproducing the observed flare trajectory in the vicinity of Sgr A*, illustrating a pass faction surpassing 90% among the investigated flare models. In particular, determining spin orientation within this model is linked to the rotation of the accretion disk. Assuming a counterclockwise accretion disk, a prograde black hole with a≥1/2 is able to reproduce the observed flare kinematics in the Galactic center. Conversely, assuming a clockwise rotation for the disk, the observations support both prograde and retrograde Kerr black holes with a large spin.
ER -