Surface velocity network with anti-solar differential rotation on the activeK-giant σ Geminorum

We demonstrate the power of the local correlation tracking technique on stellar data for the first time. We recover the spot migration pattern of the long‐period RS CVn‐type binary σ Gem from a set of six Doppler images from 3.6 consecutive rotation cycles. The resulting surface flow map suggests a weak anti‐solar differential rotation with α ≈ –0.0022 ± 0.0016, and a coherent poleward spot migration with an average velocity of 220 ± 10ms‐1. This result agrees with our recent findings from another study and could also be confirmed theoretically. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)