Detection of differential rotation in psi Cap with profile analysis

Abstract

We report detection of differential rotation on the F5 dwarf psi Cap using line profile analysis. The Fourier transform of both FeI lambda 5775 and SiI lambda 5772 are used to obtain a projected rotational velocity of v sini = (42+-1)km/s. Modelling of the Fourier transformed profiles shows that the combined effects of equatorial velocity, inclination and differential rotation dominate the line profile while limb darkening and turbulence velocities have only minor effects. Rigid rotation is shown to be inconsistent with the measured profiles. Modelling the line profiles analogous to solar differential rotation we find a differential rotation parameter of alpha = 0.15+-0.1 (15+-10%) comparable to the solar case. To our knowledge this is the first successful measurement of differential rotation through line profile analysis.Comment: 4 pages, 4 figures, accepted for publication in A&A Letter