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  Asteroseismology of evolved stars to constrain the internal transport of angular momentum: I. Efficiency of transport during the subgiant phase

Eggenberger, P., Deheuvels, S., Miglio, A., Ekström, S., Georgy, C., Meynet, G., et al. (2019). Asteroseismology of evolved stars to constrain the internal transport of angular momentum: I. Efficiency of transport during the subgiant phase. Astronomy and Astrophysics, 621: A66. doi:10.1051/0004-6361/201833447.

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Item Permalink: http://hdl.handle.net/21.11116/0000-0004-8B13-A Version Permalink: http://hdl.handle.net/21.11116/0000-0004-8B18-5
Genre: Journal Article

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 Creators:
Eggenberger, P., Author
Deheuvels, S., Author
Miglio, A., Author
Ekström, S., Author
Georgy, C., Author
Meynet, G., Author
Lagarde, N., Author
Salmon, S., Author
Buldgen, G., Author
Montalbán, J., Author
Spada, Federico1, Author              
Ballot, J., Author
Affiliations:
1Department Solar and Stellar Interiors, Max Planck Institute for Solar System Research, Max Planck Society, ou_1832287              

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Free keywords: stars: rotation / stars: oscillations / stars: interiors
 Abstract: Context. The observations of solar-like oscillations in evolved stars have brought important constraints on their internal rotation rates. To correctly reproduce these data, an efficient transport mechanism is needed in addition to the transport of angular momentum by meridional circulation and shear instability. The efficiency of this undetermined process is found to increase both with the mass and the evolutionary stage during the red giant phase. Aims. We study the efficiency of the transport of angular momentum during the subgiant phase. Methods. The efficiency of the unknown transport mechanism is determined during the subgiant phase by comparing rotating models computed with an additional corresponding viscosity to the asteroseismic measurements of both core and surface-rotation rates for six subgiants observed by the Kepler spacecraft. We then investigate the change in the efficiency of this transport of angular momentum with stellar mass and evolution during the subgiant phase. Results. The precise asteroseismic measurements of both core and surface-rotation rates available for the six Kepler targets enable a precise determination of the efficiency of the transport of angular momentum needed for each of these subgiants. These results are found to be insensitive to all the uncertainties related to the modelling of rotational effects before the post-main sequence (poMS) phase. An interesting exception in this context is the case of young subgiants (typical values of log(g) close to 4), because their rotational properties are sensitive to the degree of radial differential rotation on the main sequence (MS). These young subgiants constitute therefore perfect targets to constrain the transport of angular momentum on the MS from asteroseismic observations of evolved stars. As for red giants, we find that the efficiency of the additional transport process increases with the mass of the star during the subgiant phase. However, the efficiency of this undetermined mechanism decreases with evolution during the subgiant phase, contrary to what is found for red giants. Consequently, a transport process with an efficiency that increases with the degree of radial differential rotation cannot account for the core-rotation rates of subgiants, while it correctly reproduces the rotation rates of red giant stars. This suggests that the physical nature of the additional mechanism needed for the internal transport of angular momentum may be different in subgiant and red giant stars.

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Language(s): eng - English
 Dates: 2019
 Publication Status: Published online
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Method: Peer
 Identifiers: DOI: 10.1051/0004-6361/201833447
 Degree: -

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Title: Astronomy and Astrophysics
  Other : Astron. Astrophys.
Source Genre: Journal
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Affiliations:
Publ. Info: Les Ulis Cedex A France : EDP Sciences
Pages: - Volume / Issue: 621 Sequence Number: A66 Start / End Page: - Identifier: Other: 1432-0746
ISSN: 0004-6361
CoNE: https://pure.mpg.de/cone/journals/resource/954922828219_1