Surface velocity network with anti-solar differential rotation on the active K-giant $\ddot{I}ƒ$ Geminorum

Abstract

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 $\ddot{I}ƒ$ 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 $\hat{I}\pm \approx -0.0022\pm 0.0016$, and a coherent poleward spot migration with an average velocity of $220\pm 10$ m s${}^{-1}$. This result agrees with our recent findings from another study and could also be confirmed theoretically.

3 pages, 3 figures, conference title: 5th Potsdam Thinkshop, accepted for publication in Astronomische Nachrichten