Dynamically important magnetic fields near the event horizon of Sgr A*

Jiménez-Rosales, A.; Dexter, J.; Widmann, F.; Bauböck, M.; Abuter, R.; Amorim, A.; Berger, J. P.; Bonnet, H.; Brandner, W.; Clénet, Y.; de Zeeuw, P. T.; Eckart, A.; Eisenhauer, F.; Förster Schreiber, N. M.; Garcia, P.; Gao, F.; Gendron, E.; Genzel, R.; Gillessen, S.; Habibi, M.; Haubois, X.; Heißel, G.; Henning, T.; Hippler, S.; Horrobin, M.; Jochum, L.; Jocou, L.; Kaufer, A.; Kervella, P.; Lacour, S.; Lapeyrère, V.; Le Bouquin, J.-B.; Léna, P.; Nowak, M.; Ott, T.; Paumard, T.; Perraut, K.; Perrin, G.; Pfuhl, O.; Rodríguez-Coira, G.; Shangguan, J.; Scheithauer, S.; Stadler, J.; Straub, O.; Straubmeier, C.; Sturm, E.; Tacconi, L. J.; Vincent, F.; Fellenberg, S. von; Waisberg, I.; Wieprecht, E.; Wiezorrek, E.; Woillez, J.; Yazici, S.; Zins, G.

doi:10.1051/0004-6361/202038283

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Dynamically important magnetic fields near the event horizon of Sgr A*

MPS-Authors

/persons/resource/persons216133

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

/persons/resource/persons146381

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

/persons/resource/persons214431

Widmann, F.
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/persons225865

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

/persons/resource/persons4766

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

/persons/resource/persons4923

Förster Schreiber, N. M.
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;

/persons/resource/persons4768

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

/persons/resource/persons181377

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

/persons/resource/persons16190

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

/persons/resource/persons4782

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

/persons/resource/persons232571

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

/persons/resource/persons248280

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

/persons/resource/persons232635

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

/persons/resource/persons4650

Sturm, E.
Infrared and Submillimeter Astronomy, MPI for Extraterrestrial Physics, Max Planck Society;

/persons/resource/persons4582

Tacconi, L. J.
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/persons188252

Waisberg, I.
Infrared and Submillimeter Astronomy, MPI for Extraterrestrial Physics, Max Planck Society;

/persons/resource/persons16329

Wieprecht, E.
Infrared and Submillimeter Astronomy, MPI for Extraterrestrial Physics, Max Planck Society;

/persons/resource/persons16335

Wiezorrek, E.
Infrared and Submillimeter Astronomy, MPI for Extraterrestrial Physics, Max Planck Society;

/persons/resource/persons203013

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

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Citation

Jiménez-Rosales, A., Dexter, J., Widmann, F., Bauböck, M., Abuter, R., Amorim, A., et al. (2020). Dynamically important magnetic fields near the event horizon of Sgr A*. Astronomy and Astrophysics, 643: A56. doi:10.1051/0004-6361/202038283.

Cite as: https://hdl.handle.net/21.11116/0000-0007-EC9C-0

Abstract

We study the time-variable linear polarisation of Sgr A* during a bright near-infrared flare observed with the GRAVITY instrument on July 28, 2018. Motivated by the time evolution of both the observed astrometric and polarimetric signatures, we interpret the data in terms of the polarised emission of a compact region (“hotspot”) orbiting a black hole in a fixed, background magnetic field geometry. We calculated a grid of general relativistic ray-tracing models, created mock observations by simulating the instrumental response, and compared predicted polarimetric quantities directly to the measurements. We take into account an improved instrument calibration that now includes the instrument’s response as a function of time, and we explore a variety of idealised magnetic field configurations. We find that the linear polarisation angle rotates during the flare, which is consistent with previous results. The hotspot model can explain the observed evolution of the linear polarisation. In order to match the astrometric period of this flare, the near horizon magnetic field is required to have a significant poloidal component, which is associated with strong and dynamically important fields. The observed linear polarisation fraction of ≃30% is smaller than the one predicted by our model (≃50%). The emission is likely beam depolarised, indicating that the flaring emission region resolves the magnetic field structure close to the black hole.