Weber, Michael

Contact Email: kstrassmeier@aip.de
Institute: Astrophysikalisches Institut Potsdam, An der
Sternwarte 16, D-14482 Potsdam, Germany
First Coauthor: K. G. Strassmeier
Institute: Astrophysikalisches Institut Potsdam
Second Coauthor: A. Washuettl
Institute: Astrophysikalisches Institut Potsdam
Research URL:http://www.aip.de/groups/activity
Presenting Thesis: Yes
Subject Area: Stellar Atmospheres, Circumstellar Material
Waveband: Optical
Technique: Imaging (Doppler)
Presentation: Poster Display
Title: Doppler imaging of stellar surface structure: The differential rotation of the K giant IL Hydrae revisited
Abstract: We re-determined the differential rotation law at the surface of the K giant ILHydrae (P $_{\rm rot}{\approx}$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 $\alpha=\Omega_1/\Omega_0$=-0.27 and $1/\Delta\Omega$=50 days. This is less than half of 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 of the Sun, but based on only two Doppler images taken one year apart. This indicates, that average spot lifetimes on ILHya are on the order of a few stellar rotations.