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Sgr A* near-infrared flares from reconnection events in a magnetically arrested disc

MPS-Authors
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Dexter,  J.
Infrared and Submillimeter Astronomy, MPI for Extraterrestrial Physics, Max Planck Society;

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Jiménez-Rosales,  A.
Infrared and Submillimeter Astronomy, MPI for Extraterrestrial Physics, Max Planck Society;

/persons/resource/persons216131

Bauböck,  M.
Infrared and Submillimeter Astronomy, MPI for Extraterrestrial Physics, Max Planck Society;

/persons/resource/persons250315

Dallilar,  Y.
Infrared and Submillimeter Astronomy, MPI for Extraterrestrial Physics, Max Planck Society;

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de Zeeuw,  P. T.
Infrared and Submillimeter Astronomy, MPI for Extraterrestrial Physics, Max Planck Society;

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Eisenhauer,  F.
Infrared and Submillimeter Astronomy, MPI for Extraterrestrial Physics, Max Planck Society;

/persons/resource/persons206120

Fellenberg,  S. von
Infrared and Submillimeter Astronomy, MPI for Extraterrestrial Physics, Max Planck Society;

/persons/resource/persons214427

Gao,  F.
Infrared and Submillimeter Astronomy, MPI for Extraterrestrial Physics, Max Planck Society;

/persons/resource/persons4590

Genzel,  R.
Infrared and Submillimeter Astronomy, MPI for Extraterrestrial Physics, Max Planck Society;

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Gillessen,  S.
Infrared and Submillimeter Astronomy, MPI for Extraterrestrial Physics, Max Planck Society;

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Habibi,  M.
Infrared and Submillimeter Astronomy, MPI for Extraterrestrial Physics, Max Planck Society;

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Ott,  T.
Infrared and Submillimeter Astronomy, MPI for Extraterrestrial Physics, Max Planck Society;

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Stadler,  J.
Infrared and Submillimeter Astronomy, MPI for Extraterrestrial Physics, Max Planck Society;

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Straub,  O.
Infrared and Submillimeter Astronomy, MPI for Extraterrestrial Physics, Max Planck Society;

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Widmann,  F.
Infrared and Submillimeter Astronomy, MPI for Extraterrestrial Physics, Max Planck Society;

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Citation

Dexter, J., Tchekhovskoy, A., Jiménez-Rosales, A., Ressler, S. M., Bauböck, M., Dallilar, Y., et al. (2020). Sgr A* near-infrared flares from reconnection events in a magnetically arrested disc. Monthly Notices of the Royal Astronomical Society, 497(1), 4999-5007. doi:10.1093/mnras/staa2288.


Cite as: http://hdl.handle.net/21.11116/0000-0007-EE72-D
Abstract
Large-amplitude Sgr A* near-infrared (NIR) flares result from energy injection into electrons near the black hole event horizon. Astrometry data show continuous rotation of the emission region during bright flares, and corresponding rotation of the linear polarization angle. One broad class of physical flare models invokes magnetic reconnection. Here, we show that such a scenario can arise in a general relativistic magnetohydrodynamic simulation of a magnetically arrested disc. Saturation of magnetic flux triggers eruption events, where magnetically dominated plasma is expelled from near the horizon and forms a rotating, spiral structure. Dissipation occurs via reconnection at the interface of the magnetically dominated plasma and surrounding fluid. This dissipation is associated with large increases in NIR emission in models of Sgr A*, with durations and amplitudes consistent with the observed flares. Such events occur at roughly the time-scale to re-accumulate the magnetic flux from the inner accretion disc, ≃10 h for Sgr A*. We study NIR observables from one sample event to show that the emission morphology tracks the boundary of the magnetically dominated region. As the region rotates around the black hole, the NIR centroid and linear polarization angle both undergo continuous rotation, similar to the behaviour seen in Sgr A* flares.