Asteroseismic measurement of surface-to-core rotation in a main sequence A star, KIC 11145123

TL;DR

This study uses asteroseismology to measure the internal rotation profile of a main sequence A star, revealing nearly uniform rotation with a slightly faster surface, providing insights into stellar angular momentum transfer mechanisms.

Contribution

It presents the first robust, model-independent measurement of both core and surface rotation in a main sequence star using rotationally split pulsation modes.

Findings

Core and surface rotation periods are nearly 100 days.

Surface rotates slightly faster than the core.

Implication of a strong angular momentum transfer mechanism.

Abstract

We have discovered rotationally split core g-mode triplets and surface p-mode triplets and quintuplets in a terminal age main sequence A star, KIC 11145123, that shows both $\delta$ Sct p-mode pulsations and $\gamma$ Dor g-mode pulsations. This gives the first robust determination of the rotation of the deep core and surface of a main sequence star, essentially model-independently. We find its rotation to be nearly uniform with a period near 100 d, but we show with high confidence that the surface rotates slightly faster than the core. A strong angular momentum transfer mechanism must be operating to produce the nearly rigid rotation, and a mechanism other than viscosity must be operating to produce a more rapidly rotating surface than core. Our asteroseismic result, along with previous asteroseismic constraints on internal rotation in some B stars, and measurements of internal rotation in some subgiant, giant and white dwarf stars, has made angular momentum transport in stars throughout their lifetimes an observational science.