Fast core rotation in red-giant stars as revealed by gravity-dominated mixed modes

Author(s)

Paul G. Beck, Josefina Montalban, Thomas Kallinger, Joris De Ridder, Conny Aerts, Rafael A. García, Saskia Hekker, Marc-Antoine Dupret, Benoit Mosser, Patrick Eggenberger, Dennis Stello, Yvonne Elsworth, Søren Frandsen, Fabien Carrier, Michel Hillen, Michael Gruberbauer, Jørgen Christensen-Dalsgaard, Andrea Miglio, Marica Valentini, Timothy R. Bedding, Hans Kjeldsen, Forrest R. Girouard, Jennifer R. Hall, Khadeejah A. Ibrahim

Abstract

When the core hydrogen is exhausted during stellar evolution, the

central region of a star contracts and the outer envelope expands and

cools, giving rise to a red giant. Convection takes place over much of

the star's radius. Conservation of angular momentum requires that the

cores of these stars rotate faster than their envelopes; indirect

evidence supports this. Information about the angular-momentum

distribution is inaccessible to direct observations, but it can be

extracted from the effect of rotation on oscillation modes that probe

the stellar interior. Here we report an increasing rotation rate from

the surface of the star to the stellar core in the interiors of red

giants, obtained using the rotational frequency splitting of recently

detected `mixed modes'. By comparison with theoretical stellar models,

we conclude that the core must rotate at least ten times faster than the

surface. This observational result confirms the theoretical prediction

of a steep gradient in the rotation profile towards the deep stellar

interior.

Organisation(s)

Department of Astrophysics

External organisation(s)

Katholieke Universiteit Leuven, Université de Liège, University of Amsterdam (UvA), Université de recherche Paris Sciences et Lettres, Université de Genève, The University of Sydney, University of Birmingham, Aarhus University, Saint Mary's University, National Aeronautics & Space Administration (NASA), Radboud University, Université Paris VII - Paris-Diderot

Journal

Nature

Volume

481

Pages

55-57

ISSN

0028-0836

DOI

https://doi.org/10.1038/nature10612

Publication date

01-2012

Peer reviewed

Yes

Austrian Fields of Science 2012

103004 Astrophysics

Portal url

https://ucrisportal.univie.ac.at/en/publications/29c2d335-d7a6-43fa-88b1-0a95f984a712