Differential rotation from STELLA time series
Time-series spectroscopy has been proved to be an outstanding experience in studying differential
rotation of spotted stars. STELLA robotic observatory provides an exceptional possibility of collecting good quality densely sampled homogeneous long-term spectroscopic datasets, covering enough long time intervals for the best performance spatial and time resolution.
We use long-term STELLA spectra of three K giants, namely sigma Geminorum, KU Pegasi and v1192 Orionis, to reconstruct contiguous Doppler maps using iMap.
Then, we apply the technique of ‘average cross-correlation of time-series Doppler images’ (ACCORD) to retrieve surface differential rotation for the stars. The results nicely follow the empirical trend that slower rotators perform larger surface shear.