Deformation and differential rotation in slowly rotating young intermediate-mass stars

TL;DR

This paper uses asteroseismology to analyze the internal structure and rotation of young intermediate-mass stars, revealing diverse deformation shapes and differential rotation patterns that inform stellar models.

Contribution

It presents new measurements of stellar deformation and differential rotation in multiple stars, including unexpected prolate shapes and magnetic field indications, advancing understanding of stellar dynamics.

Findings

Most stars are oblate, consistent with rapid rotation.

One star shows a 10% faster equatorial rotation than the pole.

Some stars exhibit prolate shapes, possibly due to magnetic fields.

Abstract

Asteroseismology, the study of stellar vibrations, is a method which can probe the structure deformation and internal rotation of stars. Salient among the seismic inferences of rotation from TESS observations are TIC 408165734, whose equatorial rotation rate is 10\% faster than the pole, and TIC 307930890, which has significant radial shear and shows a decreasing spin rate outward through its envelope. We also measure structural deformation in fifteen stars, nine of which are oblate, a finding consistent with expectations for relatively fast-rotating, non-magnetic stars. The difference between polar and equatorial radii in TIC 47639058 is 130 times larger than that for the Sun. The remaining six stars display splittings consistent with a prolate shape (surprisingly), possibly indicating the presence of equatorial toroidal magnetic fields. These inferences provide constraints for numerical simulations and new insights to guide theories of $\delta$ Scuti structure and rotation.