POSTER PAPER 6.03
Doppler Imaging of Stellar Surface Structure: The Differential
Rotation of the K-giant IL Hydrae
M. Weber, K. G. Strassmeier, A. Washuettl
Institute: Astrophysikalisches Institut Potsdam
Contact Email: kstrassmeier@aip.de
Abstract:
We re-determined the differential rotation law at the surface of the K
giant IL Hydrae (Prot = 12.9 days). Using new NSO and
KPNO spectra covering five consecutive rotations in 1996 and two
rotations 15 days apart in 2000, we cross-correlate three independent
Doppler images from 1996 and two from 2000. Assuming a solar-like
differential rotation law, we derive a = Omega1/Omega0=-0.047 and 1/(Delta Omega) = 277 days. This is more than double the
solar value of 120 days and in the opposite direction,
i. e. the polar regions rotate faster than the equatorial
regions. This result is in contrast to earlier measurements showing a
weak differential rotation in the same direction as the Sun, but
based on only two Doppler images taken one year apart. This indicates,
that average spot lifetimes on IL Hya are on the order of a few
stellar rotations.
Index Keywords: HD 81410; Differential Rotation; Doppler Imaging; Starspot
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Manuscript submitted: 2001-Sep-05
"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.