Detection of Differential Rotation in Psi Cap with Profile Analysis
A. Reiners, J.H.M.M. Schmitt, & M. Kuerster
Institute: Hamburg University
Institute: European Southern Observatory
Contact Email: areiners@hs.uni-hamburg.de
Abstract:
Differential rotation has been detected on the fast rotator
Psi Cap (F5 V) using line profile analysis. The Fourier transforms of
both Fe I 5775 A and Si I 5772 A are used to obtain a projected
rotational velocity of vsinii = 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,
comparable to the solar case. To our knowledge this is the first
successful measurement of differential rotation through line profile
analysis. A check with an observable directly obtained from the
Fourier transform shows the internal consistency of our results.
Index Keywords: Psi Cap ; stellar dynamo ; differential rotation
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Manuscript submitted: 2001-Aug-24
"The Future of Cool-Star Astrophysics", 2003, Eds. A. Brown,
G. M. Harper, & T. R. Ayres.
Proceedings of 12th Cambridge Workshop on Cool Stars, Stellar Systems,
& The Sun,
© 2003 University of Colorado.