Astronomy and Astrophysics, volume 398, 647-661 (2003/2-1)
Rotation and differential rotation in field F- and G-type stars.
REINERS A. and SCHMITT J.H.M.M.
Abstract (from CDS):
We present a detailed study of rotation and differential rotation analyzing high resolution high S/N spectra of 142 F-, G- and early K-type field stars. Using Least Squares Deconvolution we obtain broadening profiles for our sample stars and use the Fourier transform method to determine projected rotational velocities vsin i. Distributions of rotational velocities and periods are studied in the HR-diagram. For a subsample of 32 stars of spectral type F0-G0 we derive the amount of differential rotation in terms of α=(ΩEquator-ΩPole)/Ω_ Equator_. We find evidence for differential rotation in ten of the 32 stars. Differential rotation seems to be more common in slower rotators, but deviations from rigid rotation are also found in some fast rotators. We search for correlations between differential rotation and parameters relevant for stellar activity and show indications against strong differential rotation in very active stars. We derive values of ΔP and ΔΩ, which support a period dependence of differential rotation. Derived lap times 2π/ΔΩ are of the order of 20d and contradict the assumption that constant lap times of the order of the solar one (∼130d) are the rule in stars that are thought to harbour magnetic dynamos.