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.
Highlights
The Sun does not rotate like a rigid body
We present projected rotational velocities and new measurements of the rotational profile of some 180 nearby stars with spectral types A-F
The strongest amount of relative differential rotation (54%) detected by line profile analysis is found among F stars
Summary
The Sun does not rotate like a rigid body. Angular rotational velocity varies with latitude (latitudinal differential rotation) and with distance from the center (radial differential rotation). Differential rotation is thought to emerge from the interaction between the turbulent motions in the convective envelope and Coriolis forces which are due to rotation. It is believed to be an important ingredient of the widely accepted solar α-Ω dynamo. Differential rotation is closely connected to magnetic activity. Based on observations made with ESO Telescopes at the La Silla Paranal Observatory under programme ID’s 074.D-0008 and 075.D-0340
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