Core-Envelope Coupling in Intermediate-Mass Core-Helium Burning Stars

Understand

Stars between two and three solar masses rotate rapidly on the main sequence, and the detection of slow core and surface rotation in the core-helium burning phase for these stars places strong constraints on their angular momentum transport and loss.

• From a detailed asteroseismic study of the mixed-dipole mode pattern in a carefully selected, representative sample of stars, we find that slow core rotation rates in the range reported by prior studies are a general phenomenon and not a selection effect.
• We show that the core rotation rates of these stars decline strongly with decreasing surface gravity during the core He-burning phase.
• We argue that this is a model-independent indication of significant rapid angular momentum transport between the cores and envelopes of these stars.