New measurements of rotation and differential rotation in A-F stars: Are there two populations of differentially rotating stars?

TL;DR

This study measures the rotation profiles of 180 A-F stars, identifying 10 with significant differential rotation and suggesting two distinct populations with different rotational characteristics.

Contribution

It provides new measurements of stellar rotation profiles and reveals potential two-population structure among differential rotators based on spectral type.

Findings

10 stars with significant differential rotation identified

Frequency of differential rotators decreases with higher temperature

Evidence suggests two populations of differential rotators separated at early-F spectral type

Abstract

We present projected rotational velocities and new measurements of the rotational profile of some 180 nearby stars with spectral types A-F. The overall broadening profile is derived analysing spectral line shape from hundreds of spectral lines by the method of least-squares deconvolution. Rigid and differential rotation can be distinguished in 56 cases. Ten stars with significant differential rotation rates are identified. As of now, 33 differential rotators detected by line profile analysis have been confirmed. The frequency of differential rotators decreases towards high effective temperature and rapid rotation. There is evidence for two populations of differential rotators with a gap in between at spectral type early-F. The gap can only partly be explained by an upper bound found for the horizontal shear of F stars. Apparently, the physical conditions of differential rotation change at early-F spectral types.