Spin down of the core rotation in red giants

Author(s)

B. Mosser, M. J. Goupil, K. Belkacem, J. P. Marques, P. G. Beck, S. Bloemen, J. De Ridder, C. Barban, S. Deheuvels, Y. Elsworth, S. Hekker, T. Kallinger, R. M. Ouazzani, M. Pinsonneault, R. Samadi, D. Stello, R. A. García, T. C. Klaus, J. Li, S. Mathur, R. L. Morris

Abstract

Context. The space mission Kepler provides us with long and

uninterrupted photometric time series of red giants. We are now able to

probe the rotational behaviour in their deep interiors using the

observations of mixed modes. Aims: We aim to measure the

rotational splittings in red giants and to derive scaling relations for

rotation related to seismic and fundamental stellar parameters.

Methods: We have developed a dedicated method for automated measurements

of the rotational splittings in a large number of red giants. Ensemble

asteroseismology, namely the examination of a large number of red giants

at different stages of their evolution, allows us to derive global

information on stellar evolution. Results: We have measured

rotational splittings in a sample of about 300 red giants. We have also

shown that these splittings are dominated by the core rotation. Under

the assumption that a linear analysis can provide the rotational

splitting, we observe a small increase of the core rotation of stars

ascending the red giant branch. Alternatively, an important slow down is

observed for red-clump stars compared to the red giant branch. We also

show that, at fixed stellar radius, the specific angular momentum

increases with increasing stellar mass. Conclusions: Ensemble

asteroseismology indicates what has been indirectly suspected for a

while: our interpretation of the observed rotational splittings leads to

the conclusion that the mean core rotation significantly slows down

during the red giant phase. The slow-down occurs in the last stages of

the red giant branch. This spinning down explains, for instance, the

long rotation periods measured in white dwarfs.

 

Appendices A and B are available in electronic form at www.aanda.org

Organisation(s)

Department of Astrophysics, Department of East Asian Studies

External organisation(s)

Université de recherche Paris Sciences et Lettres, Georg-August-Universität Göttingen, Katholieke Universiteit Leuven, Yale University, University of Birmingham, University of Amsterdam (UvA), Université de Liège, Ohio State University, The University of Sydney, Université Paris VII - Paris-Diderot, National Aeronautics & Space Administration (NASA), National Center for Atmospheric Research (NCAR)

Journal

Astronomy & Astrophysics

Volume

548

ISSN

0004-6361

DOI

https://doi.org/10.1051/0004-6361/201220106

Publication date

2012

Peer reviewed

Yes

Austrian Fields of Science 2012

103004 Astrophysics

Keywords

Portal url

https://ucris.univie.ac.at/portal/en/publications/spin-down-of-the-core-rotation-in-red-giants(14ac0271-f635-4099-a8d5-394af8908ac5).html