Doppler imaging of stellar surface structure - XVI. A time-series analysisof the moderately-rotating K1-giant sigma Geminorum

We present a simultaneous photometric and spectroscopic imaging analysis of the long-period RS CVn binary sigma Gem, covering 3.6 consecutive rotation cycles with high time resolution. From six overlapping but consecutive Dop pler maps we trace the evolution of individual spots throughout the time ra nge covered. All spots group either along a band at approximately +45 degre es latitude and a width of 30 degrees, or appear centered at the equator. N o polar spot is detected. We did not find a conclusive migration pattern fr om the cross-correlation maps from one rotation to the next and attribute t his to a masking effect of short-term spot changes.