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

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.

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Jiménez-Rosales, A.1, Author           
Dexter, J.1, Author           
Widmann, F.1, Author           
Bauböck, M.1, Author           
Abuter, R., Author
Amorim, A., Author
Berger, J. P., Author
Bonnet, H., Author
Brandner, W., Author
Clénet, Y., Author
de Zeeuw, P. T.1, Author           
Eckart, A., Author
Eisenhauer, F.1, Author           
Förster Schreiber, N. M.1, Author           
Garcia, P., Author
Gao, F.1, Author           
Gendron, E., Author
Genzel, R.1, Author           
Gillessen, S.1, Author           
Habibi, M.1, Author           
Haubois, X., AuthorHeißel, G., AuthorHenning, T., AuthorHippler, S., AuthorHorrobin, M., AuthorJochum, L., AuthorJocou, L., AuthorKaufer, A., AuthorKervella, P., AuthorLacour, S., AuthorLapeyrère, V., AuthorLe Bouquin, J.-B., AuthorLéna, P., AuthorNowak, M., AuthorOtt, T.1, Author           Paumard, T., AuthorPerraut, K., AuthorPerrin, G., AuthorPfuhl, O.1, Author           Rodríguez-Coira, G., AuthorShangguan, J.1, Author           Scheithauer, S., AuthorStadler, J.1, Author           Straub, O.1, Author           Straubmeier, C., AuthorSturm, E.1, Author           Tacconi, L. J.1, Author           Vincent, F., AuthorFellenberg, S. von1, Author           Waisberg, I.1, Author           Wieprecht, E.1, Author           Wiezorrek, E.1, Author           Woillez, J., AuthorYazici, S.1, Author           Zins, G., Author more..
Affiliations:
1Infrared and Submillimeter Astronomy, MPI for Extraterrestrial Physics, Max Planck Society, ou_159889              

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 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.

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Language(s): eng - English
 Dates: 2020-11-03
 Publication Status: Published online
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Type: -
 Identifiers: DOI: 10.1051/0004-6361/202038283
Other: LOCALID: 3284673
 Degree: -

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Title: Astronomy and Astrophysics
  Other : Astron. Astrophys.
Source Genre: Journal
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Publ. Info: France : EDP Sciences S A
Pages: - Volume / Issue: 643 Sequence Number: A56 Start / End Page: - Identifier: ISSN: 1432-0746
CoNE: https://pure.mpg.de/cone/journals/resource/954922828219_1