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Issue A&A
Volume 376, Number 1, September II 2001
Page(s) L13 - L16
Section Letters
DOI http://dx.doi.org/10.1051/0004-6361:20011023



A&A 376, L13-L16 (2001)
DOI: 10.1051/0004-6361:20011023

Detection of differential rotation in $\psi$ Cap with profile analysis

A. Reiners1, J. H. M. M. Schmitt1 and M. Kürster2

1  Hamburger Sternwarte, Universität Hamburg, Gojenbergsweg 112, 21029 Hamburg, Germany
2  European Southern Observatory, Casilla 19001, Vitacura, Santiago 19, Chile

(Received 8 June 2001 / Accepted 16 July 2001)

Abstract
We report detection of differential rotation on the F5 dwarf $\psi$ Cap using line profile analysis. The Fourier transform of both Fe I $\lambda$5775 and Si I $\lambda$5772 are used to obtain a projected rotational velocity of $v \sin{i}=42\pm1$ km s-1. 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 $\alpha=0.15\pm0.1$ ($15\pm10$% ) comparable to the solar case. To our knowledge this is the first successful measurement of differential rotation through line profile analysis.


Key words: methods: data analysis -- stars: activity -- stars: individual: $\psi$ Cap -- stars: late-type -- stars: rotation

Offprint request: A. Reiners, areiners@hs.uni-hamburg.de

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