Differential Rotation and Magnetism across the HR Diagram

Rotation and Differential Rotation of the Kepler stars

Not scheduled

132:028 (Nordita)

Talk

Speaker

Timo Reinhold (Institute for Astrophysics Goettingen)

Description

The Kepler space telescope monitors more than 160.000 stars with an unprecedented precision providing the opportunity to study stellar variability of thousands of stars. We present rotation periods for thousands of active stars in the Kepler field. In most cases a second period close to the rotation period has been detected which is considered as hint for surface Differential Rotation (DR). We show how the absolute and relative shear correlate with rotation period and effective temperature. The fraction of active stars is selected from the whole sample using the range of the variability amplitude. To detect different periods in the light curves we use the Lomb-Scargle periodogram in a prewhitening approach to achieve parameters for a global sine fit. The most dominant periods are associated to different surface rotation periods. Since most light curves are dominated by several periods we conclude that DR might be very common in active stars. Our results match observations and theoretical models but should be treated with caution. Our method cannot distinguish between the physical origins of periodicity so there might be some false positives among our periods.