Differential Rotation and Magnetism across the HR Diagram

Studying stellar rotation and magnetic activity cycles with asteroseismic measurements

Not scheduled

1m

132:028 (Nordita)

Talk

Speaker

Rafael A. Garcia Garcia (Laboratoire AIM, CEA/DSM-CNRS-Université Paris)

Description

Continuous photometric coverage of stars provided by asteroseismic space missions, are a great opportunity to study their surface rotation and stellar variability. In particular, long and uninterrupted Kepler observations of more than 3.5 years allows us to study stellar activity cycles of many stars. A surface stellar activity proxy can be built from the variance of the light curve as the spots crossing the visible disk of stars produce a modulation in stellar photometry. The higher the number of spots is, the larger the variance. Moreover, in a few dozens of fast rotating stars, we have also access to acoustic modes. We can then study the perturbations induced below the surface by the magnetic cycle in the properties of the modes, such as their amplitudes and frequencies. Although solar-like stars can have magnetic activity cycles longer than the length of current asteroseismic observations performed with CoRoT and Kepler, several authors have suggested a relation between the length of the cycles and the rotation period. Therefore, for rapidly rotating (young) stars, the cycles can be of a few years and therefore accessible to our current measurements. In this talk we propose to review some of the open questions we have and how CoRoT and Kepler measurements, with the support of ground based observations, are shedding new light onto this field.