Asteroseismic measurement of slow, nearly-uniform surface-to-core rotation in the main sequence F star KIC 9244992

TL;DR

This study uses asteroseismology to measure the nearly uniform slow rotation of the main sequence F star KIC 9244992's core and surface, revealing more efficient internal angular momentum transport than standard models predict.

Contribution

First asteroseismic measurement of the nearly uniform slow rotation in a main sequence F star, providing new insights into stellar interior angular momentum transport.

Findings

Core and surface rotation are nearly equal at ~64-66 days.

Star is at an advanced main sequence stage with reduced central hydrogen.

Results suggest stronger angular momentum transport than standard theories.

Abstract

We have found a rotationally split series of core g-mode triplets and surface p-mode multiplets in a main sequence F star, KIC 9244992. Comparison with models shows that the star has a mass of about 1.45 M$_\odot$, and is at an advanced stage of main sequence evolution in which the central hydrogen abundance mass fraction is reduced to about 0.1. This is the second case, following KIC 11145123, of an asteroseismic determination of the rotation of the deep core and surface of an A-F main-sequence star. We have found, essentially model-independently, that the rotation near the surface, obtained from p-mode splittings, is 66 d, slightly slower than the rotation of 64 d in the core, measured by g-mode splittings. KIC 9244992 is similar to KIC 11145123 in that both are near the end of main-sequence stage with very slow and nearly uniform rotation. This indicates the angular momentum transport in the interior of an A-F star during the main sequence stage is much stronger than that expected from standard theoretical formulations.