Volume 408, Number 3, September IV 2003
|Page(s)||1103 - 1113|
|Published online||17 November 2003|
Doppler imaging of stellar surface structure
XX. The rapidly-rotating single K2-giant HD 31993 = V1192 Orionis
Astrophysical Institute Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany e-mail: email@example.com
2 Institut für Astronomie, Universität Wien, Türkenschanzstr. 17, 1180 Wien, Austria e-mail: firstname.lastname@example.org
Corresponding author: K. G. Strassmeier, email@example.com
Accepted: 1 July 2003
We present two Doppler images from two consecutive stellar rotations of the single K2-giant HD 31993. Each Doppler image is reconstructed from spectra obtained within a single stellar rotation. With its 25-day rotational period and a radius of ≈18 solar radii, HD 31993 is considered a very rapidly rotating star and thus allows the application of the Doppler-imaging technique, despite the unusually long period. All maps reveal 7 isolated, predominantly low-latitude spots with a temperature difference, photosphere minus spot, of just ≈200 K. No polar spot or high-latitude activity above, say, +60° is seen. A large warm feature is detected at high latitude and is believed to be real. These spots act as tracers for a cross correlation analysis and yield a clear signature of anti-solar differential surface rotation, i.e. the polar regions rotating faster than the equator, with corresponding to a lap time of ≈200 days. A detailed parameter study is carried out to verify the reality of the HD 31993 maps.
Key words: stars: activity / stars: imaging / stars: individual: HD31993 / stars: late-type / stars: starspots
© ESO, 2003
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