Understanding angular momentum transport in red giants: the case of KIC 7341231

¹ Laboratoire AIM Paris-Saclay, CEA/DSM/IRFU/SAp – CNRS – Université Paris Diderot, Centre de Saclay, 91191 Gif-sur-Yvette Cedex, France
e-mail: tugdual.ceillier@cea.fr
² Observatoire de Genève, Université de Genève, 51 chemin des Maillettes, 1290 Sauverny, Suisse

Received: 14 March 2013
Accepted: 21 May 2013

Abstract

Context. Thanks to recent asteroseismic observations, it has been possible to infer the radial differential rotation profile of subgiants and red giants.

Aims. We want to reproduce the observed rotation profile of the early red giant KIC 7341231 through modeling and constrain the physical mechanisms responsible for angular momentum transport in stellar interiors.

Methods. We computed models of KIC 7341231 including a treatment of shellular rotation, and we compared the rotation profiles obtained with the one derived from observations. We then modify some modeling parameters in order to quantify their effect on the obtained rotation profile. Moreover, we mimicked a powerful angular momentum transport during the main sequence and studied its effect on the evolution of the rotation profile during the subgiant and red giant phases.

Results. We show that meridional circulation and shear mixing alone produce a rotation profile for KIC 7341231 that is too steep compared to the observed one. An additional mechanism is then needed to increase the internal transport of angular momentum. We find that this undetermined mechanism has to be efficient not only during the main sequence but also during the much quicker subgiant phase. Moreover, we point out the importance of studying the whole rotational history of a star to explain its rotation profile during the red giant evolution.