Heidelberg Joint Astronomical Colloquium

Speaker Ansgar Reiners
Title Rotation and activity in low-mass stars

We know from the Sun that stars can generate magnetic fields, which cause sunspots, high-energy X-rays, UV emission, and a plethora of other activity phenomena including mass ejections that can reach Earth. On other stars, and perhaps the young Sun, activity is even believed to handicap the development of life. The Sun's magnetic field is connected to its rotation through a gigantic dynamo, of which only little is understood. Other stars are known to rotate a lot faster than the Sun, and rapid rotation generates higher magnetic field strengths in stars - just as we know from our bicycles. Interestingly, stellar magnetic fields back-react on rotation; rapid rotators are being braked very efficiently by the field they generate.

I will give an overview on the evolution of stellar angular momentum evolution and the recent advances in magnetic field measurements in low-mass stars. I will particularly show why low-mass stars seem to suffer much less rotational braking.