Asteroseismology as a probe of magnetism in stars

Dr. Lisa Bugnet (Flatiron Institute)

One of the “legacy" results of the Kepler mission is the interestingly low rotation rate of the core of subgiant (SG) and red giant (RG) stars, which is about 10 times lower than predicted with the current theory for the transport of angular momentum by purely hydrodynamical mechanisms. This discrepancy points out an order of magnitude issue concerning the understanding of the evolution of the stellar angular momentum in evolved Solar-like stars, a very ubiquitous problem shared by stars of all types and ages. The recent discovery of very low-amplitude dipolar oscillations in a significant fraction of the observed SGs and RGs also points out our misunderstanding of physical processes inside the radiative interiors of evolved Solar-like stars. We thus seek for a missing process taking place inside the core of evolved Solar-like stars, efficient to extract angular momentum from the core to the surface and to perturbate stellar oscillations. Internal magnetic fields are one of the most serious candidates that are currently studied to solve both problems. I will present how we can search for magnetic fields inside evolved low-mass stars with Asteroseismology, and what we can learn about the internal dynamics of these stars.