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Issue A&A
Volume 384, Number 1, March II 2002
Page(s) 155 - 162
Section Formation, structure and evolution of stars
DOI http://dx.doi.org/10.1051/0004-6361:20011801



A&A 384, 155-162 (2002)
DOI: 10.1051/0004-6361:20011801

On the feasibility of the detection of differential rotation in stellar absorption profiles

A. Reiners and J. H. M. M. Schmitt

Hamburger Sternwarte, Universität Hamburg, Gojenbergsweg 112, 21029 Hamburg, Germany

(Received 24 September 2001 / Accepted 12 December 2001 )

Abstract
Stellar differential rotation invokes subtle effects on line absorption profiles which can be best studied in the Fourier domain. Detailed calculations of the behavior of Fourier transformed profiles with respect to varying differential rotation, limb darkening and inclination angles are presented. The zero positions of the Fourier transform are found to be very good tracers of differential rotation. The ratio of the first two zero positions $\sigma_{2}/\sigma_{1}$ can be easily measured and is a reliable parameter to deduce the amount of differential rotation. It is shown that solar-like differential rotation (equatorial regions have larger angular velocity then polar regions) has an unambigious signature in the Fourier domain and that in certain cases it can easily be distinguished from limb darkening effects. A simple procedure is given allowing the determination of the amount of differential rotation by the knowledge of the first two zero positions of a line profile's Fourier transform alone (i.e., without the need for thorough atmospheric modelling), under the assumption of a linear limb darkening law with a limb darkening coefficient of $\epsilon = 0.6$ .


Key words: stars: rotation -- line: profiles

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

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© ESO 2002


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