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

Abstract

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